Liquid crystal display

ABSTRACT

A liquid crystal display is furnished with: a liquid crystal display element having a pair of substrates, to which alignment members are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates; an alignment mechanism for providing at least two different director configurations simultaneously on different arbitrary regions used for display in the liquid crystal layer; and a reflection film provided to at least one of the different arbitrary regions showing different director configurations; wherein the different arbitrary regions showing different director configurations are used for a reflection display section for showing reflection display and a transmission display section for showing transmission display, respectively. Examples of the alignment mechanism include an alignment film to which the alignment treatment is applied in different orientations in the reflection display section and transmission display section, respectively, an insulation film having different film thicknesses in the reflection display section and transmission display section, and so forth.

FIELD OF THE INVENTION

[0001] The present invention relates to liquid crystal displays used forinformation systems, such as word processors and notebook-type personalcomputers, video equipment of various kinds, video game machines,portable VCRs, digital cameras, etc. More particularly, the presentinvention relates to liquid crystal displays used indoors and outdoors,or in automobiles, air-planes, marine vessels, etc. where a variety ofambient light conditions occurs.

BACKGROUND OF THE INVENTION

[0002] Conventionally, CRTs (Cathode Ray Tubes), EL(Electroluminescence) elements, PDPs (Plasma Display Panels), etc. havebeen put into practical use as displays of the light emissive type inwhich display contents can be overwritten electrically.

[0003] However, since this type of displays emit display light and usethe same directly for the display, there arises a problem that theirpower consumption is quite large. Further since a light-emitting surfaceof the displays of this type serves as a display surface having highreflectance, if the displays of this type are used under thecircumstances where ambient light is brighter than the luminance, forexample, in direct sunlight, there always occurs a phenomenon known as“wash-out” in which the display light can not be observed.

[0004] On the other hand, liquid crystal displays have been put intopractical use as color displays which display characters and/or imagesnot by emitting the display light, but by adjusting an amount oftransmitted light from a particular light source. These liquid crystaldisplays include a transmission type and a reflection type.

[0005] Of the two types, particularly popular are the liquid crystaldisplays of the transmission type which employ a light source called“back light” at the back side, namely, behind the liquid crystal cell.Since the liquid crystal displays of the transmission type areadvantageous in thinness and lightness, they have been used indiversified fields. On the other hand, the liquid crystal displays ofthe transmission type consume a large amount of power to keep the backlight turned ON. Thus, regardless of the advantage that only a smallamount of power is consumed to adjust transmittance of the liquidcrystal, a relatively large amount of power is consumed as a whole.

[0006] However, the liquid crystal displays of the transmission type(that is, color liquid crystal displays of the transmission type) washout less frequently compared with the displays of the light emissivetype. This is because, in the color liquid crystal displays of thetransmission type, the reflectance on the display surface of a colorfilter layer is reduced by the reflectance reducing technique using ablack matrix.

[0007] Nevertheless, it becomes too difficult to observe the displaylight on the color liquid crystal displays of the transmission type whenthey are used under the circumstances where the ambient light is verystrong and the display light is relatively weak. This problem can beeliminated by using brighter back light, but this solution raisesanother problem that the power consumption is further increased.

[0008] Unlike the displays of the light emissive type and liquid crystaldisplays of the transmission type, the liquid crystal displays of thereflection type show the display using the ambient light, therebyobtaining display light proportional to an amount of the ambient light.Thus, the liquid crystal displays of the reflection type areadvantageous in a principle that they do not wash out, and when used ina very bright place in direct sunlight, for example, the display can beobserved all the more sharply. Further, the liquid crystal displays ofthe reflection type do not use the back light for the display, andtherefore, have another advantage that the power for keeping the backlight turned ON can be saved. For the above reasons, the liquid crystaldisplays of the reflection type are particularly suitable as the devicesfor the outdoor use, such as portable information terminals, digitalcameras, and portable video cameras.

[0009] However, since these conventional liquid crystal displays of thereflection type use the ambient light for the display, the displayluminance largely depends on the surrounding environment, and when usedunder the circumstances where the ambient light is weak, there arises aproblem that the display content can not be observed. Particularly, incase that a color filter is used for realizing the color display, thecolor filter absorbs the light and the display becomes darker. Thus,when used under these circumstances, the above problem becomes moreapparent.

[0010] To eliminate the above problem, a lighting device called “frontlight” has been developed as an auxiliary light, so that the liquidcrystal displays of the reflection type can be used under thecircumstances where the ambient light is weak. Since the liquid crystaldisplays of the reflection type have a reflection layer behind theliquid crystal layer, they can not use the back light as do the liquidcrystal displays of the transmission type. For this reason, the lightingdevice (front light) lights the liquid crystal displays of thereflection type from the front side, that is, from the display surfaceside.

[0011] On the other hand, liquid crystal displays, employing atransflective film which transmits a part of incident light and reflectsthe rest, have been put into practical use as the liquid crystaldisplays which can be used under the circumstances where the ambientlight is weak while maintaining the advantages of the liquid crystaldisplays of the reflection type. The liquid crystal displays using boththe transmitted light and reflected light are generally referred to asthe liquid crystal displays of the transflective type.

[0012] For example, Japanese Laid-open Patent Application No.218483/1984 (Tokukaisho No. 59-21843) (Japanese Patent Application No.92885/1983 (Tokugansho No. 58-92885)) discloses a liquid crystal displayof the transflective type which modulates the brightness by the TN(Twisted Nematic) mode, STN (Super-Twisted Nematic) mode, etc., whichare known as the liquid crystal display modes for modulating theluminance of the transmitted light. Also, Japanese Laid-open PatentApplication No. 318929/1995 (Tokukaihei No. 7-318929) discloses a liquidcrystal display of the transflective type, in which a transflective filmis provided in close proximity to the liquid crystal layer. Further,Japanese Laid-open Patent Application No. 160878/1994 (Tokukaihei No.6-160878) (U.S. Pat. Nos. 5,598,285 and 5,737,051) discloses a liquidcrystal display of the transmission type adopting the in-plane switchingmethod as a technique for realizing a wider range of viewing angles.However, since the liquid crystal display of the transflective typedisclosed in Japanese Patent Application No. 218483/1984 (Tokukaisho No.59-218483) has the transflective film behind the liquid crystal cellseen from the viewer's side, there occur the following problems (1) and(2).

[0013] (1) It is very difficult to set the brightness which affects avisibility of the display device. More specifically, when the brightnessof the liquid crystal display of the transflective type is setadequately for the reflection display, the brightness is set high, sothat it can be used under the circumstances where the ambient light isinsufficient. However, if the brightness is set high by using apolarization plate having high transmittance in the TN method, forexample, a contrast ratio, which is defined as a quotient obtained bydividing the brightness in the light display by the brightness in thedark display, becomes too low for the transmission display, therebydeteriorating the visibility. Conversely, when the brightness of theliquid crystal display of the transflective type is set adequately forthe transmission display, it is preferable to set the brightness in sucha manner as to raise the contrast ratio. However, in this case, thebrightness becomes too low for the reflection display, therebydeteriorating the visibility as well.

[0014] (2) In the reflection display, since the display is observed byreflecting the light having passed through the liquid crystal layersandwiched by the two substrates by the reflection film provided behindthe liquid crystal cell, there occurs parallax (double image) and theresolution deteriorates, thereby making high-resolution display verydifficult.

[0015] Also, in the liquid crystal display of the transflective typedisclosed in Japanese Laid-open Patent Application No. 318929/1995(Tokukaihei No. 7-318929) , since the transflective film is used as thereflection film, there arises another problem that there is no opticaldesign such that can be suitable for both the reflection display sectionand transmission display section.

[0016] Further, although the in-plane switching method disclosed inJapanese Laid-open Patent Application No. 160878/1994 (Tokukaihei No.6-160878) is employed in the liquid crystal displays of the transmissiontype, the director configuration of the liquid crystal on thecomb-shaped electrode does not contribute to the display. This is notbecause, in most cases, the electrode lines are made of metal that doesnot transmit light, but because the director configuration of the liquidcrystal is not changed sufficiently for the transmission display.

SUMMARY OF THE INVENTION

[0017] Thus, to eliminate the above problems, the inventors of thepresent invention tried to apply the display method capable ofeliminating the parallax and employed in the liquid crystal displays ofthe reflection type to the liquid crystal displays of the transflectivetype. More specifically, the inventors conducted an assiduous study byapplying the two following methods to the transflective display:

[0018] (a) the GH (Guest-Host) method for filling liquid crystalcomposition blended with a dichroic dye into the liquid crystal layer;and

[0019] (b) the reflection type liquid crystal display method using asingle polarization plate (hereinafter, referred to as the singlepolarization plate method).

[0020] To apply the above two display methods (a) and (b) whicheliminate the parallax to the liquid crystal displays of thetransflective type, the reflection layer is provided to touch or almosttouch the liquid crystal layer, and a transmission opening is madethrough the reflection layer to use the transmitted light for thedisplay in addition to the reflected light.

[0021] Then, the study revealed the following problems In case of (a) GHmethod, when a concentration of the dichroic dye blended with the liquidcrystal composition is adjusted adequately for the reflection display,the brightness is sufficiently high but the contrast ratio becomes toolow in the transmission display section, thereby failing to obtainsatisfactory display. On the other hand, when a concentration of thedichroic dye blended with the liquid crystal composition is adjustedadequately for the transmission display, the contrast ratio issufficiently high in the transmission display section, but thebrightness becomes too low in the reflection display section, therebyfailing to obtain satisfactory display.

[0022] Also, in case of (b) single polarization plate method, thedirector configuration of the liquid crystal and a thickness of theliquid crystal layer which determine the optical characteristics, avoltage applied to the liquid crystal for driving the same, etc. are setadequately for either the reflection display section or the transmissiondisplay realized by additionally providing a polarization plate or thelike behind the display surface (double polarization plate method).

[0023] Firstly, the display in the transmission display section when thethickness of the liquid crystal layer is set adequately for thereflection display will be explained. In this case, an amount of changein the polarization state caused when the director configuration of theliquid crystal layer is changed by an external field, such as anelectric field, is about a strength such that can realize a satisfactorycontrast ratio when incident light from the front, that is, from thedisplay surface side, passes through the liquid crystal layer and exitsto the display surface side by passing through the liquid crystal layeragain. However, when set in this manner, an amount of the change of thepolarization state of the light having passed through the liquid crystallayer is not sufficient in the transmission display section. Thus, evenif the polarization plate used for the transmission display alone isprovided behind the liquid crystal cell seen from the viewer's side inaddition to the polarization plate used for the reflection display andprovided to the viewer's side of the liquid crystal cell, that is, thedisplay surface side, the display in the transmission display section isnot satisfactory. In other words, when the director configurations(thickness of the liquid crystal layer, director configuration of theliquid crystal, etc.) of the liquid crystal layer are set to be suitablefor the reflection display, in the transmission display section, eitherthe brightness is not sufficient or even if the brightness issufficient, the transmittance does not decrease in the dark display,thereby failing to attain a sufficient contrast ratio for the display.

[0024] To be more specific, in case of the reflection display, thedirector configuration of the liquid crystal in the liquid crystal layeris controlled by means of a voltage applied to the liquid crystal layerto impart a phase difference of about ¼ wavelength to the light passingthrough the liquid crystal layer only once. When the transmissiondisplay is shown with the voltage modulation such that imparts a ¼wavelength phase modulation to the light passing through the liquidcrystal layer set in such a manner as to impart the above-specifiedphase difference to the light passing through the same, if thetransmittance of the transmission display section for the dark displayis lowered sufficiently, about half the luminance of the light isabsorbed by the polarization plate at the light outgoing side when thetransmission display section shows the light display, thereby failing toobtain satisfactory light display. If optical elements, such as apolarization plate and a phase difference compensation plate, areprovided to increase the brightness in the light display in thetransmission display section, the brightness in the dark display in thetransmission display section is increased to about half the brightnessin the light display, and the resulting contrast ratio is notsatisfactory for the display.

[0025] Next, the display in the reflection display section, in case thatthe director configurations of the liquid crystal layer are set to besuitable for the transmission display, will be explained. In case thatthe reflection display is shown when the liquid crystal layer is setadequately for the transmission display, the director configuration ofthe liquid crystal must be controlled by the voltage modulation in sucha manner that the polarization state of the light passing through theliquid crystal layer only once is modulated between the two polarizationstates which are orthogonal each other. The two orthogonal polarizationstates include two linearly polarized light beams having oscillationplanes intersecting at right angles, two circularly polarized lightbeams of right and left circularly polarization, or two ellipticallypolarized light beams having the same ellipticity whose major axisorientations intersect at right angles, thereby having opposite rotationdirections in their respective photo-electric fields. To realize themodulation of the polarization state in any combination of the above twopolarization states being orthogonal each other, a voltage must bemodulated in such a manner that the liquid crystal layer imparts a phasedifference of ½ wavelength to the light passing through the same. Whenthe polarization state of the light is modulated by any combination ofthe two orthogonal polarization states in the above manner, satisfactorybrightness and contrast ratio can be attained in the transmissiondisplay optionally, by the function of the polarization plate, with thehelp of the phase difference compensation plate.

[0026] However, when the liquid crystal layer is set to realize theabove control, the reflectance in the reflection display is changed fromthe light display to the dark display and to the light display againwhile the transmittance in the transmission display is changed once fromthe light display to the dark display. Thus, the same display, that is,either the light or dark display, can not be realized simultaneously inthe reflection display section and transmission display section by thesame liquid crystal alignment changing means (for example, the thicknessof the liquid crystal layer is equal, the initial director configurationis identical, and the driving voltage is equal). The problems raised inthe methods (a) and (b) are also raised with the liquid crystal displayof the transflective type disclosed in aforementioned Japanese Laid-openPatent Application No. 318929/1995 (Tokukaihei No. 7-318929).

[0027] In addition, a pressure detecting input device (touch panel)superimposed on the liquid crystal display has light reflectingproperties, thereby posing a problem that the visibility isdeteriorated. This problem is particularly obvious in the liquid crystaldisplays of the reflection type.

[0028] Also, in general, a front light unit used to improve thevisibility of the liquid crystal displays of the reflection type underthe circumstances where the ambient light is weak has a planar lightpipe structure. Thus, the display content is observed through this lightpipe, and there arises a problem that the visibility is deteriorated.

[0029] The present invention is devised to solve the above problems, andit is therefore an object of the present invention to provide a liquidcrystal display with excellent visibility, capable of showinghigh-resolution display while using both the reflected light andtransmitted light for the display. It is another object of the presentinvention to provide a liquid crystal display with excellent visibility,capable of showing high-resolution color display while using both thereflected light and transmitted light for the display.

[0030] The inventors of the present invention continued an assiduousstudy to fulfill the above and other objects, and achieved the presentinvention when they discovered that the cause of the problems occurredin the conventional liquid crystal displays applying either the GHmethod or polarization plate method is that the director configurationof the liquid crystal layer is set identical in the transmission displaysection and reflection display section at the same time.

[0031] Here, the director configuration of the liquid crystal layerindicates not only the director defined as orientation of the liquidcrystal molecules at a specific point in the liquid crystal layer, butalso the variation of the director field with respect to the positionalong the normal axis of the liquid crystal layer.

[0032] To be more specific, to fulfill the above and other objects, aliquid crystal display of the present invention is a liquid crystaldisplay furnished with a liquid crystal display element having a pair ofsubstrates, to which alignment members are provided to their respectiveopposing surfaces, and a liquid crystal layer sandwiched by the pair ofsubstrates, characterized in that:

[0033] alignment mechanism for providing at least two different directorconfigurations simultaneously on different arbitrary regions used fordisplay in the liquid crystal layer is provided;

[0034] a reflecting member is provided to at least one of the differentarbitrary regions showing different director configurations; and

[0035] the different arbitrary regions showing different directorconfigurations are used for a reflection display section for showingreflection display and a transmission display section for showingtransmission display, respectively.

[0036] According to the above arrangement, the director configuration ofthe liquid crystal can be different simultaneously. Thus, for example,an amplitude of modulation in an opti-physical quantity, such as anamount of absorbed light (absorbance) in case that a light absorber likea dichroic dye is used for the display, and a phase difference in casethat optical anisotropy is used for the display, can be changedseparately in each region having a different director configuration ofthe liquid crystal. Thus, according to the above arrangement, thetransmittance or reflectance based on an amplitude of modulation in anopti-physical quantity in response to the director configuration of theliquid crystal layer can be obtained, thereby making it possible to setthe optical parameters of the transmission display section and those ofthe reflection display section independently. Consequently, according tothe above arrangement, it has become possible to provide a liquidcrystal display of the transflective type with excellent visibility,capable of showing high-resolution display while using both thereflected light and transmitted light for the display.

[0037] Also, to fulfill the above and other objects, a liquid crystaldisplay of the present invention is a liquid crystal display furnishedwith a liquid crystal display element having a pair of substrates, towhich alignment members are provided to their respective opposingsurfaces, and a liquid crystal layer sandwiched by the pair ofsubstrates, characterized in that:

[0038] a region used for display in the liquid crystal layer is composedof regions having at least two different thicknesses of the liquidcrystal layer;

[0039] the regions having at least two different thicknesses are usedfor a reflection display section and a transmission display section,respectively;

[0040] a reflecting member is provided at least to the reflectiondisplay section; and

[0041] the thickness of the liquid crystal layer is thinner in thereflection display section than in the transmission display section.

[0042] According to the above arrangement, the transmittance orreflectance based on an amplitude of modulation in an opti-physicalquantity in the regions having different thicknesses of the liquidcrystal layer can be obtained, thereby making it possible to set thetransmission display section and reflection display sectionindependently. Thus, according to the above arrangement, it has becomepossible to provide a liquid crystal display of the transflective typewith excellent visibility, capable of showing high-resolution displaywhile using both the reflected light and transmitted light for thedisplay.

[0043] According to the present invention, satisfactory display can beshown on both the reflection display section and transmission displaysection by providing the above arrangement to the liquid crystaldisplay. However, there is an optimal ratio of the reflection displaysection to the transmission display section for showing satisfactorydisplay, and this optimal ratio varies depending on whether colordisplay or monochrome display is desired, or whether the display isshown mainly by the reflection display or transmission display.

[0044] In the liquid crystal display of the present invention, in casethat both the reflection display section and the transmission displaysection show color display, it is preferable that an area of thereflection display section accounts for 30% or above and 90% and less ofa total of areas of the reflection display section and the transmissiondisplay section.

[0045] When the color display is shown on the liquid crystal display ofthe present invention in the above manner, besides the liquid crystallayer, design of the color filter layer, which plays an important rolein color reproduction, is critical. According to the study of theinventors of the present invention, the liquid crystal display of thetransflective type will be used in typical two styles.

[0046] One is a style that mainly shows the transmission display ingeneral use and uses the reflection display supplementarily, so that thewash-out can be prevented under the lighting environment where theambient light is very strong, and therefore, can be used extensively indiversified lighting environments compared with the displays of theluminous type or the liquid crystal displays of the transmission type.The other is a style that mainly shows the reflection display in generaluse by exploiting the advantages of the reflection display that thepower consumption is small and the lighting device known as the backlight is turned ON only when used under the circumstances where thelighting is weak. Hence, like in the former style, this style can beused extensively in diversified lighting environments.

[0047] In the former style (the style showing the transmission displaymainly), by providing a color filter having a transmission color atleast in the transmission display section of the regions making up theregion of each pixel in at least one of the pair of substrates, it hasbecome possible to provide a liquid crystal display with excellentvisibility, capable of showing high-resolution color display while usingboth the reflected light and transmitted light for the display.

[0048] When the color display is shown in the above manner, it iseffective if the color filter having a transmission color is provided atleast to the transmission display section in each pixel, and in thereflection display section, either no color film is used or a colorfilter having the same brightness as the brightness of the color filterprovided to the transmission display section or a color filter having atransmission color brighter than the brightness in the color filterprovided to the transmission display section, is provided at leastpartially.

[0049] In the latter style (the style showing the reflection displaymainly), by providing a color filter having a transmission color atleast in the reflection display section of the regions making up thedisplay region of each pixel in at least one of the pair of substrates,it has become possible to provide a liquid crystal display withexcellent visibility, capable of showing high-resolution color displaywhile using both the reflected light and transmitted light for thedisplay.

[0050] When the color display is shown in the above manner, it iseffective if the color filter having a transmission color is provided toat least the reflection display section in each pixel, and in thetransmission display section, either no color film is used or a colorfilter having chroma as good as the chroma of the color filter providedto the reflection display section or a color filter having atransmission color with better chroma than the chroma of the colorfilter provided to the reflection display section, is provided at leastpartially.

[0051] According to the above arrangement, it has become possible toprovide a liquid crystal display with excellent visibility, capable ofshowing a high-resolution color display while using both the reflectedlight and transmitted light for the display.

[0052] For a fuller understanding of the nature and advantages of theinvention, reference should be made to the ensuing detailed descriptiontaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0053]FIG. 1 is a cross section showing a major portion of a liquidcrystal display in accordance with Embodiment 1 of the presentinvention;

[0054]FIG. 2 is a view showing display characteristics of a liquidcrystal display of Example 1;

[0055]FIG. 3 is a view showing display characteristics of liquid crystaldisplays of Comparative Examples 2 and 3, respectively;

[0056]FIG. 4 is a cross section showing a major portion of a liquidcrystal display in accordance with Embodiment 2 of the presentinvention;

[0057]FIG. 5 is a view explaining a definition of a crossed rubbingangle;

[0058]FIG. 6 is a view showing display characteristics of a liquidcrystal display of Example 2;

[0059]FIG. 7 is a view showing display characteristics of a liquidcrystal display of Example 3;

[0060]FIG. 8 is a view showing display characteristics of a liquidcrystal display of Example 4;

[0061]FIG. 9 is a view showing display characteristics of a liquidcrystal display of Example 5;

[0062]FIG. 10 is a view showing display characteristics of a liquidcrystal display of Example 6;

[0063]FIG. 11 is a view showing display characteristics of a liquidcrystal display of Example 7;

[0064]FIG. 12 is a view showing display characteristics of a liquidcrystal display of Comparative Example 3;

[0065]FIG. 13 is a view showing display characteristics of a liquidcrystal display of Example 8;

[0066]FIG. 14 is a view showing display characteristics of a liquidcrystal display of Comparative Example 4;

[0067]FIG. 15 is a view showing display characteristics of a liquidcrystal display of Comparative Example 5;

[0068]FIG. 16 is a view showing display characteristics of a liquidcrystal display of Example 9;

[0069]FIG. 17 is a view showing the steps of the alignment treatmentapplied to the substrates used for a liquid crystal display inaccordance with Embodiment 4 of the present invention;

[0070] FIGS. 18(a) through 18(e) are cross sections schematicallyshowing the alignment treatment steps of FIG. 17;

[0071]FIG. 19 is a view showing display characteristics of a liquidcrystal display of Example 10;

[0072]FIG. 20 is a view showing display characteristics of a liquidcrystal display of Example 11;

[0073]FIG. 21(a) is a cross section showing a major portion of a liquidcrystal display of Example 12 when no voltage is applied;

[0074]FIG. 21(b) is a cross section showing the major portion of theliquid crystal display of FIG. 21(a) when a voltage is applied;

[0075]FIG. 22 is a view showing display characteristics of a liquidcrystal display of Example 12;

[0076]FIG. 23(a) is a plan view showing a major portion of a TFT elementsubstrate for realizing a liquid crystal display of thetransmission-main transflective type in accordance with Embodiment 7 ofthe present invention;

[0077]FIG. 23(b) is a view showing a driving electrode of a reflectiondisplay section on the TFT element substrate of FIG. 23(a);

[0078]FIG. 23(c) is a view showing a transparent pixel electrode on theTFT element substrate of FIG. 23(a);

[0079]FIG. 24 is a cross section of the TFT element substrate taken online A-A′ of FIG. 23(a);

[0080]FIG. 25 is a cross section of the TFT element substrate taken online B-B′ of FIG. 23(a);

[0081]FIG. 26(a) is a plan view showing a major portion of the liquidcrystal display of the transmission-main transflective type inaccordance with Embodiment 7 of the present invention, and it is apartial cutaway view of a color filter substrate showing an alignment ofcolor filters formed on the color filter substrate used in the aboveliquid crystal display of the transmission-main transflective type withrespect to a transmission display opening of a driving electrode formedin the reflection display section on the TFT element substrate of FIG.23(a);

[0082]FIG. 26(b) is a cross section of the color filter substrate ofFIG. 26(a);

[0083]FIG. 27 is a cross section showing a major portion of the liquidcrystal display taken on line C-C′ of FIG. 26(a);

[0084]FIG. 28 is a plan view showing a major portion of a TFT elementsubstrate for realizing a liquid crystal display of the reflection-maintransflective type in accordance with Embodiment 7 of the presentinvention;

[0085]FIG. 29(a) is a plan view showing a major portion of the liquidcrystal display of the reflection-main transflective type in accordancewith Embodiment 7 of the present invention, and it is a partial cutawayview of a color filter substrate showing an alignment of color filtersformed on the color filter substrate used in the above liquid crystaldisplay of the reflection-main transflective type with respect to atransmission display opening of a driving electrode formed in thereflection display section on the TFT element substrate of FIG. 28;

[0086]FIG. 29(b) is a cross section of the color filter substrate ofFIG. 29(a);

[0087]FIG. 30 is a contour plot showing a relation of adapted luminancewhich imparts perceived brightness of an equivalent value versus sampleluminance;

[0088]FIG. 31 is a view showing characteristics of a relation ofilluminance versus perceived brightness in a liquid crystal display ofthe transflective type in accordance with Embodiment 8 of the presentinvention; and

[0089]FIG. 32 is a cross section schematically showing an arrangement ofa major portion of a liquid crystal display incorporating an inputdevice in accordance with Embodiment 11 of the present invention.

DESCRIPTION OF THE EMBODIMENTS

[0090] A liquid crystal display of the present invention ischaracterized in that the director configuration of the liquid crystalcan take different states respectively in the reflection display sectionand transmission display section at the same time. Here, the directorconfiguration of the liquid crystal means not only the director definedas orientation of the liquid crystal molecules at a particular point inthe liquid crystal layer, but also the variation of the director fieldwith respect to the position along the normal axis of the liquid crystallayer. Thus, in the present invention, methods of realizing differentdirector configurations of the liquid crystal in the reflection displaysection and transmission display section and alignment mechanisms usedfor these methods are classified into three categories, and each will beexplained separately below.

[0091] In a first category method, the liquid crystal is given differentdirector configurations in the reflection display section andtransmission display section by means of an alignment mechanism formedto impose a specific condition of the liquid crystal layer differentlyin the reflection display section and transmission display section.

[0092] To be more specific, examples of the first category methodinclude:

[0093] (1) using an alignment mechanism that twists the director of theliquid crystal at totally different twist angles in the reflectiondisplay section and transmission display section;

[0094] (2) using an alignment mechanism that greatly changes the tiltangle of the director of the liquid crystal with respect to thesubstrates;

[0095] (3) providing liquid crystal materials of different kinds in thereflection display section and transmission display section; and

[0096] (4) blending different kinds of dyes with the liquid crystalmaterial at different concentrations in the transmission display sectionand reflection display section (in this case, a liquid crystal materialof the same kind may be used in the transmission display section andreflection display section).

[0097] The liquid crystal display of the present invention is furnishedwith the mechanism used for implementing the above methods as thealignment mechanism of the present invention. The first category methodand the alignment mechanism used for the first category method may be acombination of any of the above example methods (1) through (4), anddifferent director configurations of the liquid crystal can be realizedin the reflection display section and transmission display section bythe above example methods and the alignment mechanism used for theseexample methods.

[0098] In a second category method, the liquid crystal is givendifferent director configurations in the reflection display section andtransmission display section by display content overwriting means foroverwriting the display content with a time lapse (in other words, thealignment mechanism that makes the director configurations of the liquidcrystal different in the transmission display section and reflectiondisplay section is a display content overwriting means). The displaycontent overwriting means adopted in the second category method can beany of the existing display overwriting means.

[0099] More specifically, examples of the second category methodinclude:

[0100] (5) overwriting the director configuration of the liquid crystalby using different electrodes in the transmission display section andreflection display section as the alignment mechanism, in other words,applying different voltages as the display content overwriting meansdirectly to the reflection display section and transmission displaysection;

[0101] (6) applying substantially different voltages to the reflectiondisplay section and transmission display section from the sameelectrode. In this case, the liquid crystal is given with differentdirector configurations in the reflection display section andtransmission display section driven by a common electrode by providingan insulation body (for example, an insulation film) having differentlayer thicknesses in the reflection display section and transmissiondisplay section between the liquid crystal layer and the electrodedriving the same; and

[0102] (7) making the directions of the electric fields different in thereflection display section and transmission display section. In casethat the display is shown by changing the in-plane alignment directionof the liquid crystal of the liquid crystal layer by means of anelectrode group provided in parallel with one of the substratessandwiching the liquid crystal layer for supplying different potentialsto the liquid crystal layer, the director configurations of the liquidcrystal differ greatly at a region between the electrodes and a regionon the electrode. Thus, these regions having different directorconfigurations of the liquid crystal may be used for the reflectiondisplay and transmission display, respectively. Further, a method ofapplying different potentials to the liquid crystal layer alignedperpendicularly to the substrates by the same electrode group may beadopted. In case of adopting the second category method, the electrodesor insulation body used for implementing the above example methods, or acombination thereof corresponds to the alignment mechanism of thepresent invention, and naturally, the resulting liquid crystal displayis furnished with such alignment mechanism.

[0103] In a third category method, the director configurations of theliquid crystal do not differ greatly, but the thicknesses of the liquidcrystal layer, which are factors that determine the opticalcharacteristics, differ in the reflection display section andtransmission display section. To implement the third category method, aninsulation film having different thicknesses in the reflection displaysection and transmission display section, substrates having differentlayer thicknesses or shapes in the reflection display section andtransmission display section, etc. are used as the above alignmentmechanism.

[0104] In case of adopting the third category method, the directorconfiguration of the liquid crystal may be twisted uniformly like in theTN method adopted in the liquid crystal display employing twopolarization plates, for example. In this case, the directorconfiguration of the liquid crystal is parallel to the substratessandwiching the liquid crystal layer, and the director is twisted whilechanging its direction in the plane of one of the substrates inaccordance with a distance from that substrate. When this directorconfiguration of the liquid crystal is adopted in the reflection displaysection and transmission display section by varying the thickness of theliquid crystal layer, satisfactory display can be realized both in thereflection display section and transmission display section, because theoptical characteristics vary with the thickness of the liquid crystallayer.

[0105] Also, in the GH method, since varying the thickness of the liquidcrystal layer can offer substantially the same effect as the effectobtained in case of changing the concentration of the dye, satisfactorydisplay can be realized both in the reflection display section andtransmission display section, even when the director configurations ofthe liquid crystal are substantially the same in the reflection displaysection and transmission display section.

[0106] As has been explained, the method for realizing differentdirector configurations of the liquid crystal in the reflection displaysection and transmission display section and the alignment mechanismused for this method are classified into three categories, and theliquid crystal display method used in the liquid crystal display of thepresent invention realized by the above method and alignment mechanismis not especially limited, and can be selected from the methods using achange of the director configuration of the liquid crystal for thedisplay. Examples of the liquid crystal display method applicable in thepresent invention include: a mode using the nematic phase of the liquidcrystal composition for the display, such as the TN method, STN method,nematic bistable mode, vertical alignment mode, hybrid alignment mode,and ECB (Electrically Controlled Birefringence) mode. Also, a mode usingscattering, such as the polymer dispersing type liquid crystal mode anddynamic scattering method, can be used as the above liquid crystaldisplay method. Further, the surface stabilized ferroelectric liquidcrystal display method using ferroelectric liquid crystal compositionand the thresholdless switching anti-ferroelectric liquid crystaldisplay method using anti-ferroelectric liquid crystal can be used asthe above liquid crystal display method of the present invention,because they also use a change of the director configuration of theliquid crystal for the display.

[0107] In case of adopting the third category method, the liquid crystaldisplay method used in the present invention can be a method of usingmodulation of the optical rotatory polarization like the TN method, amethod of using the modulation of the retardation like the ECB mode, ora method of modulating light absorption (absorbance) like the GH method.In case of adopting the third category method, besides the abovemethods, any method is applicable, provided that the thickness of theliquid crystal layer is a critical factor for determining the opticalcharacteristics, and provided that making the liquid crystal layer thickin the transmission display section and thin in the reflection displaysection can offer an effect of realizing satisfactory display.

[0108] As has been discussed, the liquid crystal display of the presentinvention is furnished with a liquid crystal display element having apair of substrates, to which alignment members (alignment means) areprovided to their respective opposing surfaces, and a liquid crystallayer sandwiched by the pair of substrates, and it is arranged in such amanner that: it is furnished with alignment mechanism for imparting atleast two different director configurations to arbitrary and differentareas in the liquid crystal layer used for the display simultaneously; areflecting member (reflecting means) is provided in at least one of theregions showing the different director configurations in the liquidcrystal layer; and the regions showing the different directorconfigurations are used as a reflection display section for showingreflection display and a transmission display section for showingtransmission display, respectively. This arrangement makes it possibleto obtain transmittance or reflectance based on an amplitude ofmodulation in an opti-physical quantity in response to the directorconfiguration of the liquid crystal layer, thereby realizing a highcontrast ratio without causing any parallax. Consequently, not only canthe visibility under dark circumstances be improved, but alsosatisfactory visibility can be obtained even when the ambient light isstrong.

[0109] To change an amplitude of modulation in an opti-physical quantity(such as absorption of light and a phase difference caused by opticalanisotropy) in the reflection display section and transmission displaysection independently, even if the alignment direction of the liquidcrystal determined by the applied voltage is oriented to substantiallythe same direction across a region of the liquid crystal layer used forthe display, regions having different thicknesses of the liquid crystallayer can attain substantially the same effect as the effect obtainedwhen the alignment direction of the liquid crystal layer is changed inthese regions. For this reason, another liquid crystal display of thepresent invention is furnished with a liquid crystal display elementhaving a pair of substrates, to which alignment members (alignmentmeans) are provided to their respective opposing surfaces, and a liquidcrystal layer sandwiched by the pair of substrates, and it is arrangedin such a manner that:

[0110] a region used for display in the liquid crystal layer is composedof regions having at least two different thicknesses of the liquidcrystal layer;

[0111] the regions having at least two different thicknesses are usedfor a reflection display section and a transmission display section,respectively;

[0112] a reflecting member (reflecting means) is provided at least tothe reflection display section; and

[0113] the thickness of the liquid crystal layer is thinner in thereflection display section than in the transmission display section.

[0114] This arrangement also makes it possible to obtain transmittanceor reflectance based on an amplitude of modulation in an opti-physicalquantity in regions having different thicknesses of the liquid crystallayer. Accordingly, the transmission display section and reflectiondisplay section can be set independently. Thus, according to the abovearrangement, a high contrast ratio can be attained without causing anyparallax, and not only can the visibility under dark circumstances beimproved, but also satisfactory visibility can be obtained even when theambient light is strong.

[0115] A liquid crystal display realizing satisfactory reflectiondisplay and transmission display by changing the thickness of the liquidcrystal layer in the reflection display section and transmission displaysection will be explained mainly in Embodiments 1 and 2 below.

Embodiment 1

[0116] Mainly referring to FIG. 1, an example liquid crystal displayadopting the Δn method will be explained in the present embodiment.

[0117]FIG. 1 is a cross section of a major portion of the liquid crystaldisplay in accordance with the present embodiment. As shown in thedrawing, the liquid crystal display includes a liquid crystal cell 100(liquid crystal display element), and optionally, a back light 13(lighting device) serving as back light means. The liquid crystal cell100 and back light 13 are provided sequentially in this order from theviewer's (user's) side.

[0118] As shown in the drawing, the liquid crystal cell 100 is composedof a liquid crystal layer 1 sandwiched by an electrode substrate 101(first substrate) and an electrode substrate 102 (second substrate). Theelectrode substrate 101 has an alignment film 2 on a surface touchingthe liquid crystal layer 1 (an interface between the first substrate andthe liquid crystal layer 1), and the electrode substrate 102 has analignment film 3 on a surface touching the liquid crystal layer 1 (aninterface between the second substrate and the liquid crystal layer 1).

[0119] The electrode substrate 101 is composed of a substrate 4 made of,for example, a light transmitting glass substrate on which are formed anelectrode 6 (voltage applying means) for applying a voltage to theliquid crystal layer 1, and the electrode 6 is covered with thealignment film 2 (alignment mechanism) to which the rubbing treatmenthas been applied.

[0120] On the other hand, the electrode substrate 102 provided in such amanner as to oppose the electrode substrate 101 through the liquidcrystal layer 1 is composed of a light transmitting substrate 5 on whichare formed counter electrodes 7 (voltage applying means) opposing theelectrode 6 through an insulation film 11 for applying a voltage to theliquid crystal layer 1.

[0121] The insulation film 11 is made in such a manner as to havedifferent film thicknesses in regions corresponding to a region of theliquid crystal layer 1 used for the display, so that the above region ofthe liquid crystal layer 1 used for the display has at least twodifferent thicknesses of the liquid crystal layer (herein, exactly twodifferent thicknesses). To be more specific, the insulation film 11 ismade thinner in the region corresponding to the transmission displaysection 10 than in the region corresponding to the reflection displaysection 9.

[0122] In the region of the electrode substrate 102 corresponding to thereflection display section 9, a reflection film 8 (reflecting means) isformed to cover the electrodes 7, and further, the alignment film 3(alignment member, alignment mechanism) to which the rubbing treatmenthas been applied is formed to cover the electrodes 7 and reflection film8.

[0123] Here, each of the electrodes 6 and 7 is a transparent electrodemade of ITO (Indium Tin Oxide), for example. Also, a voltage is appliedto the electrodes 6 and 7 to apply an electric field in the liquidcrystal layer 1. Thus, the display is controlled by a voltage applied inaccordance with the display content.

[0124] Also, the reflection film 8 has light reflecting properties, andis made of metal, such as aluminum or silver, or composed of dielectricmulti-layer film mirror. In case that the reflection film 8 is made of aconducting material, the reflection film 8 may also serve as anelectrode instead of the electrodes 7. In other words, the reflectionfilm 8 may be a reflective pixel electrode serving both as a liquidcrystal driving electrode for driving the liquid crystal layer 1 and thereflecting means. Further, the reflection film 8 may be a colorreflection film which reflects light having a wavelength in a rangeselected from the visible light, as the case may be.

[0125] It should be appreciated that the materials and producing methodsof each member forming the electrode substrates 101 and 102 are notlimited to the above disclosure, and any known material and typicalmethod are applicable. Also, the arrangement of the liquid crystaldisplay is not limited to the above-described arrangement. For example,it may be arranged in such a manner that voltages are applied to theelectrodes 6 and 7 of the reflection display section 9 and transmissiondisplay section 10 directly from an exterior of the liquid crystal cell100 in the form of a signal from a touch panel (pressed coordinatedetecting type input means) or the like, which will be explained inembodiments below. Also, active elements, such as TFT elements and MIMelements, may be provided as the switching elements.

[0126] As shown in FIG. 1, the electrode substrates 101 and 102 arebonded to each other with a sealing agent or the like in such a mannerthat their respective alignment films 2 and 3 oppose each other, andliquid crystal composition is filled into a space therebetween, wherebythe liquid crystal layer 1 is formed.

[0127] The back light 13 is provided behind the liquid crystal cell 100seen from the viewer's (user's) side, that is, at the back side of theelectrode substrate 102. The back light 13 is mainly composed of a lightsource 13 a and a light pipe 13 b. For example, the light source 13 a isprovided along the side surface of the light pipe 13 b, and accordingly,the light pipe 13 b receives light emitted from the light source 13 a onthe side surface where it is provided, and emits the received light toan object, namely, the liquid crystal cell 100. Here, any existinglighting device can be used as the back light 13.

[0128] In the above-arranged liquid crystal display, the reflectiondisplay section 9 on which is formed the reflection film 8 shows thedisplay by controlling the reflection luminance of the ambient lightincident on the display surface from the substrate 4 side, that is fromthe viewer's side, by changing the director configuration of the liquidcrystal. The transmission display section 10 on which is formed noreflection film 8 shows the display by controlling the luminance of thetransmitted light incident on the display surface from the substrate 5side by changing the director configuration of the liquid crystal. Inthis case, light emitted from the back light 13 provided behind theliquid crystal cell 100 may be used, as the case may be.

[0129] As has been explained, the liquid crystal display of FIG. 1 isassembled in such a manner as to have different thicknesses of theliquid crystal layer in the reflection display section 9 andtransmission display section 10. Consequently, the present liquidcrystal display has substantially different director configurations ofthe liquid crystal in the reflection display section 9 and transmissiondisplay section 10.

[0130] Here, the arrangement of the liquid crystal display havingdifferent thicknesses in the reflection display section 9 andtransmission display section 10 will be explained in the following.

[0131] The liquid crystal layer can be given different thicknesses inthe reflection display section 9 and transmission display section 10,for example, by providing the insulation film 11 having differentthicknesses in the reflection display section 9 and transmission displaysection 10 as shown in FIG. 1.

[0132] In order to vary the thickness of the liquid crystal layer in thereflection display section 9 and transmission display section 10, it issufficient if at least one of the substrates (electrode substrates 101and 102) sandwiching the liquid crystal is arranged in the above manner.

[0133] Therefore, the insulation film 11 is not necessarily provided onthe substrate 4 and it can be provided on the substrate 5 instead. Evenin this case, the reflection film 8 is provided on the substrate 5 onthe electrode substrate 102 side (that is, opposing side to the displaysurface side (electrode substrate 101 side) through the liquid crystallayer 1).

[0134] In the liquid crystal display of FIG. 1, the thickness of theliquid crystal layer is changed in the reflection display section 9 andtransmission display section 10 by changing the thickness of theinsulation film 11 in a region corresponding to the reflection displaysection 9 and a region corresponding to the transmission display section10. However, the same can be realized by forming the substrate 4 or 5 itself in exactly the same shape as the insulation film 11 of FIG. 1.

[0135] When the thickness of the insulation film 11 is changed in theregion corresponding to the reflection display section 9 and the regioncorresponding to the transmission display section 10, the insulationfilm 11 on the region corresponding to the transmission display section10 is made thinner than the insulation film 11 on the regioncorresponding to the reflection display section 9 as shown in FIG. 1, orthe insulation film 11 is formed on the region corresponding to thereflection display section 9 alone, and not on the region correspondingto the transmission display section 10.

[0136] Further, the thickness of the liquid crystal layer in thereflection display section 9 or in the transmission display section 10is kept constant by providing spacers (not shown) to the liquid crystallayer 1 or by any other applicable means. For example, when sphericalspacers are provided to the liquid crystal layer 1, the thickness of thethinner liquid crystal layer in the reflection display section 9 isalmost as large as the diameter of the spacers.

[0137] The liquid crystal layer 1 sandwiched by a pair of the substratesprepared in the above manner, that is, the electrode substrates 101 and102, is made of the liquid crystal composition as previously mentioned.As the liquid crystal display method using the liquid crystal layer 1,the GH method may be used, in which the liquid crystal compositionprepared by blending a dichroic dye 12 with liquid crystal is used asshown in FIG. 1, and the director configuration of the liquid crystaland the alignment direction of the dichroic dye 12 are changedsimultaneously upon application of an electric field in the liquidcrystal layer 1, so that the display is shown using the variance of theabsorption coefficient caused by the dichroism.

[0138] Next, the following will explain, with reference to FIG. 1, theaction of the liquid crystal layer 1 in the GH method, and the displayprinciple in case that the thicknesses of the liquid crystal layer aredifferent in the reflection display section 9 and transmission displaysection 10.

[0139] When the display is shown on the liquid crystal display of FIG.1, the display is shown in the transmission display section 10 byletting light emanated from the back light 13 or the like behind theliquid crystal layer 1 pass through the liquid crystal layer 1 only onceand go out from the display surface as the display light as is indicatedby an arrow. Here, the dichroic dye 12 blended in the liquid crystalcomposition in the liquid crystal layer 1 changes its light absorbancein response to the director configuration of the liquid crystal. Thus,when the liquid crystal is aligned in parallel with the display surface(electrode substrate 101) as shown in a transmission display section 10a (which is referred to as planer alignment, hereinafter), the dichroicdye 12 in this region absorbs most of the light passing through theliquid crystal layer 1, and the transmission display section 10 showsthe dark display. On the other hand, when the liquid crystal is alignedperpendicular to the display surface (electrode substrate 101) as shownin a transmission display section 10 b, (which is referred to as thevertical alignment), the dichroic dye 12 absorbs a smaller amount of thelight, and the transmission display section 10 shows the light display.

[0140] By contrast, the reflection display section 9 uses the lightincident on the display surface from the viewer's side for the display.To be more specific, as is indicated by an arrow, the light incident onthe display surface passes through the liquid crystal layer 1 isreflected by the reflection film 8, passes through the liquid crystallayer 1 again, and exits from the display surface as the display light.Here, when the liquid crystal is aligned in parallel with the displaysurface as shown in a reflection display section 9 a, the dichroic dye12 in this region absorbs most of the light, and the reflection displaysection 9 shows the dark display. On the other hand, when the liquidcrystal is aligned perpendicular to the display surface as shown in areflection display section 9 b, the dichroic dye 12 in this regionabsorbs less amount of the light, and the reflection display section 9shows the light display.

[0141] Thus, the light display and dark display can be shown bycontrolling the director configuration of the liquid crystal bysupplying a potential difference between the electrodes 6 and 7. In thiscase, the initial director configuration of the liquid crystal is notespecially limited. For example, the liquid crystal may be aligned inparallel with the display surface or twisted further when no voltage isapplied. Conversely, the liquid crystal may be aligned perpendicular tothe display surface when no voltage is applied. In the former case(parallel when no voltage is applied or further with a twist), liquidcrystal having positive dielectric constant anisotropy can be used. Onthe other hand, in the latter case, (perpendicular when no voltage isapplied), liquid crystal having negative dielectric constant anisotropycan be used. As has been explained, the initial director configurationof the liquid crystal is not especially limited, but it is necessary toadjust the thickness of the insulation film 11 in such a manner as tosecure a thickness of the liquid crystal layer suitable for the directorconfiguration of the liquid crystal to be used.

[0142] Here, for ease of production of the liquid crystal layer 1,liquid crystal layer 1, as in typical liquid crystal displays, ispreferably provided continuously across the reflection display section 9and transmission display section 10 or a plurality of display pixels, asshown in FIG. 1.

[0143] Even when the liquid crystal layer 1 is provided across thereflection display section 9 and transmission display section 10, if thethicknesses of the liquid crystal layer are different in the reflectiondisplay section 9 and transmission display section 10, a distance thelight travels by passing through the liquid crystal layer 1 only once inthe transmission display section 10 to serve as the display light in theend can be set equal to a distance the light travels by passing andreturning through the liquid crystal layer 1 in the reflection displaysection 9.

[0144] Thus, the reflection brightness in the reflection display section9 and the transmission brightness in the transmission display section 10can be set to substantially the same level, and the contrast ratios inthe reflection display section 9 and transmission display section 10 canbe also set to substantially the same value. In other words, in the GHmethod using the light absorption by the dichroic dye 12, providingdifferent thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 can offersubstantially the same effect as the effect offered by changing theconcentration of the dye, and therefore, by so doing, the adequateconcentration of the blended dichroic dye 12 in the reflection displaysection 9 and the adequate concentration of the blended dichroic dye 12in the transmission display section 10 can be set to substantially thesame value. Consequently, the reflection display section 9 andtransmission display section 10 can show satisfactory displaysimultaneously both in the reflection display section 9 and transmissiondisplay section 10 by means of the liquid crystal layer 1 providedacross the reflection display section 9 and transmission display section10. In short, both the display contrast ratio and brightness in thelight display become substantially equal in the reflection displaysection 9 and transmission display section 10.

[0145] Herein, “brightness” is defined as a ratio of the incident lighton the liquid crystal layer 1 observed by the viewer as the displaylight in either the reflection display section 9 or transmission displaysection 10, and “contrast ratio” is defined as the quotient obtained bydividing the brightness in the light display by the brightness in thedark display.

[0146] Generally, the contrast ratio suitable for the transmissiondisplay must be higher than the contrast ratio suitable for therefection display. Thus, in order to realize satisfactory display,compared with a case of setting the equal contrast ratio in thereflection display section 9 and transmission display section 10 tosatisfy the above requirement, it is more effective to set the contrastratio higher in the transmission display section 10 than in thereflection display section 9 by setting the thickness of the liquidcrystal layer larger in the transmission display section 10 than in thereflection display section 9.

[0147] In the following, the liquid crystal display of the presentembodiment will be explained based on the above-described displayprinciple and with reference to FIGS. 1 through 3 by way of an exampleand comparative examples for purposes of explanation only, without anyintention as a definition of the limits of the invention.

EXAMPLE 1

[0148] Explained in the present example is a liquid crystal displayemploying the liquid crystal layer 1 adopting the GH method, in whichthe liquid crystal having the negative dielectric constant anisotropyaligns substantially perpendicular to the display surface when novoltage is applied to the liquid crystal layer 1 and tilts with respectto the display normal when a voltage is applied to the liquid crystallayer 1. First, the following will explain a method of manufacturing theliquid crystal display.

[0149] Initially, a 140 nm-thick ITO film is sputtered over thetransparent substrate 4, which is etched by photolithography, wherebythe electrode 6 (transparent electrode) of a predetermined pattern isformed. Here, a glass substrate is used as the substrate 4.

[0150] Next, a vertical aligning alignment film is provided to thesubstrate 4 by the offset printing on the surface where the electrode 6is formed, and the substrate 4 is baked at 200° C. in an oven, wherebythe alignment film 2 is formed. Subsequently, the alignment treatment isapplied to the alignment film 2 by means of rubbing, and as aconsequence, the electrode substrate 101 which serves as the substrateon the viewer's side is produced.

[0151] The vertical aligning alignment film originally has theproperties such that align the liquid crystal along the normal directionof the film surface, and the alignment treatment like the rubbingchanges the properties to the properties such that tilt the directorconfiguration of the liquid crystal by several degrees with respect tothe normal direction. After a voltage is applied to the liquid crystallayer 1, the tilt thus conferred tilts the director configuration of theliquid crystal much further toward the above alignment treatmentdirection.

[0152] In the meantime, insulation photosensitive resin is applied overthe substrate 5 by spin coating, and UV rays are irradiated to thephotosensitive resin masked in such a manner that no photosensitiveresin is left in the transmission display section 10, while a 3 μm-thicklayer of the photosensitive resin is formed in the reflection displaysection 9, whereby a predetermined pattern of the insulation film 11 isformed. The pattern edge portion of the insulation film 11 is made insuch a manner as to form gentle steps, so that the electrode 7 whichwill be formed later will not be broken by a difference in steps of theinsulation film 11. As with the substrate 4, a transparent glasssubstrate is used as the substrate 5.

[0153] Further, a 140 nm-thick ITO film is sputtered over the substrate5 on the surface where the insulation film 11 is formed, over which a200 nm-thick aluminum film, which will serve as a light reflectiveelectrode, is sputtered. Then, the aluminum film thus formed ispatterned by photolithography and dry etching in such a manner as toleave the aluminum film in the reflection display section 9 alone (wherethe photosensitive resin was left when the photosensitive resin waspatterned to form the insulation film 11), whereby the reflection film 8is formed. Further, the ITO film beneath the reflection film 8 is etchedby photolithography to form the electrodes 7 (transparent electrode) ofa predetermined pattern.

[0154] Subsequently, the alignment film 3 is formed over the substrate 5on the surface where the electrodes 7 and reflection film 8 are formedin the same manner as the alignment film 2 formed on the electrodesubstrate 101 serving as the substrate on the viewer's side. Then, thealignment treatment is applied to the alignment film 3 by means ofrubbing, whereby the electrode substrate 102 is produced.

[0155] Then, as a sealing agent, sealing resin (not shown) is providedaround one of the electrode substrates 101 and 102 produced in the abovemanner, and plastic spherical spacers having a diameter of 4.5 μm arescattered over the other electrode substrate on the surface where thealignment film is formed. Then, as shown in FIG. 1, the electrodesubstrates 101 and 102 are placed to oppose each other with theirelectrode surfaces inside, and the sealing resin is cured under appliedpressure, whereby a liquid crystal cell for filling is produced. Fillingspaces (thicknesses of the liquid crystal layer 1) into which the liquidcrystal will be filled in the refection display section 9 andtransmission display section 10 of the liquid crystal cell for fillingwere measured by means of the reflected light spectrum, and were 4.5 μmacross and 7.5 μm across, respectively.

[0156] Further, a concentration of the dichroic dye 12, blended with theliquid crystal having the negative dielectric constant anisotropy toproduce the liquid crystal composition filled in the liquid crystal cellfor filling is adjusted in such a manner that a satisfactory contrastratio can be attained both in the reflection display section 9 andtransmission display section 10. Further, a chiral dopant for impartingtwist to the director configuration of the liquid crystal is added tothe liquid crystal composition, so that, with the alignment treatmentapplied to the alignment films 2 and 3, the chiral dopant imparts thesame twist to the director configuration of the liquid crystal in theliquid crystal layer 1 sandwiched by the electrode substrates 101 and102 above and beneath in the reflection display section 9 andtransmission display section 10 when a voltage is applied for the darkdisplay. Then, the liquid crystal cell for filling is filled with theliquid crystal by means of vacuum injection, whereby the liquid crystaldisplay is assembled.

[0157] A voltage was applied to the liquid crystal layer 1 whilemeasuring the reflectance of the reflection display section 9 andtransmittance of the transmission display section 10 of the liquidcrystal display thus obtained through a microscope, and the displaycharacteristics graphed in FIG. 2 were obtained. The voltage applied tothe liquid crystal layer 1 is a rectangular pulse inverting every 17msec. In the drawing, the horizontal axis represents a root mean squarevalue of the applied voltage, and the vertical axis represents thebrightness (reflectance or transmittance). Also, in the drawing, a curve111 represents the voltage dependence of the reflectance in thereflection display section 9 and a curve 112 represents the voltagedependence of the transmittance in the transmission display section 10.

[0158] As the curves 111 and 112 reveal, the brightness (reflectance ortransmittance) in the reflection display section 9 and transmissiondisplay section 10 of the above liquid crystal display decreases with anincreasing applied voltage. That is, when the applied voltage is 1.8V,the reflectance of the reflection display section 9 and transmittance ofthe transmission display section 10 are 55% and 52%, respectively, andwhen the applied voltage is increased to 5V, both decrease to 11 and10%, respectively.

[0159] In other words, in the above liquid crystal display, both thereflection display section 9 and transmission display section 10 canrealize the display with excellent visibility, attaining high brightnessexceeding 50% in the light display and a contrast ratio of about 5.

COMPARATIVE EXAMPLE 1

[0160] A comparative example with respect to Example 1 will be explainedin the following. In the present comparative example, a comparativeliquid crystal display adopting the GH method was assembled in the samemanner as Example 1 except that the thicknesses of the liquid crystallayer were equal in the reflection display section 9 and transmissiondisplay section 10.

[0161] More specifically, in the present comparative example, theinsulation film 11 formed over the substrate 5 in Example 1 was omitted,so that the liquid crystal display was assembled in such a manner thatthe thickness of the liquid crystal layer was 4.5 μm in both thereflection display section 9 and transmission display section 10. Inother words, a comparative liquid crystal cell for filling was produced,in which the reflection display section 9 and transmission displaysection 10 are flat on both the electrode substrates opposing andsandwiching the liquid crystal layer 1 above and beneath, and the liquidcrystal composition blended with the dichroic dye 12 and chiral dopantused in Example 1 were also filled into the comparative liquid crystalcell for filling, whereby the comparative liquid crystal display wasassembled.

[0162] The reflectance of the reflection display section 9 andtransmittance of the transmission display section 10 of the abovecomparative liquid crystal display were measured in the same manner asExample 1, and the resulting display characteristics are graphed in FIG.3.

COMPARATIVE EXAMPLE 2

[0163] In the present comparative example, a comparative liquid crystaldisplay was assembled in such a manner that liquid crystal compositionhaving higher concentration of the dichroic dye 12 than the one inComparative Example 1 was filled into a comparative liquid crystal cellfor filling of the same type as the one used in Comparative Example 1,so that the brightness and contrast ratio become optimal for thetransmission display section 10.

[0164] The reflectance of the reflection display section 9 andtransmittance of the transmission display section 10 of the abovecomparative liquid crystal display were measured in the same manner asExample 1, and the resulting display characteristics are also graphed inFIG. 3.

[0165] In FIG. 3, the horizontal axis represents a root mean squarevalue of the applied voltage, and the vertical axis represents thebrightness (reflectance or transmittance). Also, in the drawing, a curve121 represents the voltage dependence of the reflectance in thereflection display section 9 and a curve 122 represents the voltagedependence of the transmittance in the transmission display section 10in Comparative Example 1, whereas a curve 123 represents the voltagedependence of the reflectance in the reflection display section 9 and acurve 124 represents the voltage dependence of the transmittance in thetransmission display section 10 in Comparative Example 2.

[0166] As the curves 121 and 122 reveal, the brightness (reflectance andtransmission) in the reflection display section 9 and transmissiondisplay section 10 of the comparative liquid crystal display ofComparative Example 1 decreases with an increasing applied voltage. Thatis, when the applied voltage is 1.8V, the reflectance in the reflectiondisplay section 9 and transmittance in the transmission display section10 are 55% and 66%, respectively. When the applied voltage is increasedto 5V, both decrease to 11% and 22%, respectively.

[0167] In other words, in the comparative liquid crystal display ofComparative Example 1, high brightness exceeding 50% and a satisfactorycontrast ratio of about 5 were attained in the reflection displaysection 9, whereas in the transmission display section 10, highbrightness was attained but a contrast ratio was as low as 3, therebydeteriorating the display quality. This happens because the thickness ofthe liquid crystal layer 1 is equal in the reflection display section 9and transmission display section 10.

[0168] Also, as the curves 123 and 124 reveal, the brightness(reflectance and transmission) of the reflection display section 9 andtransmission display section 10 of the comparative liquid crystaldisplay of Comparative Example 2 decreases with an increasing appliedvoltage. That is, when the applied voltage is 1.8V, the reflectance ofthe reflection display section 9 and the transmittance of thetransmission display section 10 are 29% and 51%, respectively. When theapplied voltage is increased to 5V, both decrease to 3% and 10%,respectively.

[0169] In other words, in the comparative liquid crystal display ofComparative Example 2, high brightness exceeding 50% and a satisfactorycontrast ratio of about 5 were attained in the transmission displaysection 10, whereas in the reflection display section 9, a contrastratio as high as 10 was attained but the brightness was below 30%, andthe display shown thereon was dark. This happens because the thicknessof the liquid crystal layer 1 is equal in the reflection display section9 and transmission display section 10.

[0170] The above comparison of Example 1 with Comparative Examples 1 and2 reveals that, with the liquid crystal display adopting the GH method,it is effective to set the thickness of the liquid crystal layer 1larger in the transmission display section 10 than in the reflectiondisplay section 9 to make the contrast ratio of the transmission displaysection 10 as high as or higher than the contrast ratio of thereflection display section 9.

Embodiment 2

[0171] The liquid crystal display of Embodiment 1 adopts the GH method,but liquid crystal displaying methods other than the GH method are alsoapplicable. For example, another applicable method is shown in FIG. 4,in which the substrates 4 and 5 are sandwiched by polarization plates 14and 15, so that the retardation or optical rotatory polarization (whichare collectively referred to as polarization converting function) of theliquid crystal layer 1 is used for the display.

[0172] In the present embodiment, a liquid crystal display using thepolarization converting function will be explained with reference toFIG. 4 mainly. Hereinafter, like components are labeled with likereference numerals with respect to Embodiment 1, and, for ease ofexplanation, the description of these components is not repeated here.

[0173]FIG. 4 is a cross section showing a major portion of the liquidcrystal display of the present embodiment. The liquid crystal display ofFIG. 4 includes a liquid crystal cell 200 (liquid crystal element), andoptionally, the back light 13 (lighting device), which are sequentiallyprovided in this order from the viewer's (user's) side.

[0174] As shown in FIG. 4, the liquid crystal cell 200 includes theliquid crystal layer 1 sandwiched by an electrode substrate 201 (firstsubstrate) and another electrode substrate 202 (second substrate). Theelectrode substrate 201 has the alignment film 2 on a surface touchingthe liquid crystal layer 1 (an interface between the first substrate andthe liquid crystal layer 1), and the electrode substrate 202 has thealignment film 3 on a surface touching the liquid crystal layer 1 (aninterface between the second substrate and the liquid crystal layer 1).Further, the liquid crystal cell 200 includes a phase differencecompensation plate 16 and the polarization plate 14 at the outside ofthe electrode substrate 201 (the opposite side from the side facing theelectrode substrate 202), and a phase difference compensation plate 17and the polarization plate 15 at the outside of the electrode substrate202 (the other side across the side opposing the electrode substrate201). The phase difference compensation plates 16 and 17 are used onlywhen necessary.

[0175] Phase difference compensation plates of various kinds, such as astretched polymer film, a polymer film of fixed orientation of itsliquid crystalline phase, and a liquid crystal polymer film, can be usedas the phase difference compensation plates 16 and 17 used optionally inthe present embodiment. The optical functions of the phase differencecompensation plates 16 and 17 are used to (1) prevent the coloring oftencaused when the phase difference compensation plates 16 and 17 areomitted, (2) change the dependence of the brightness on the potentialdifference between the electrodes 6 and 7, (3) change the viewing anglecharacteristics, etc.

[0176] Also, the electrode substrate 201 is composed of the substrate 4made of, for example, a light-transmitting glass substrate on which isformed the electrode 6 for applying a voltage to the liquid crystallayer 1, and the electrode 6 is covered with the alignment film 2 towhich the rubbing treatment has been applied.

[0177] On the other hand, the other electrode substrate 202 provided tooppose the electrode substrate 201 through the liquid crystal layer 1 iscomposed of the light-transmitting substrate 5 on which are formed theelectrodes 7 for applying a voltage to the liquid crystal layer 1 ascounter electrodes opposing the electrode 6 through the insulation film11. Note that, however, the liquid crystal display of FIG. 4 is arrangedin such a manner that the electrodes 7 in the reflection display section9 and the electrodes 7 in the transmission display section 10 areelectrically isolated, so that a voltage is applied to each separatelyfrom outside the liquid crystal cell. The reflection film 8 is formed onthe electrode substrate 202 at a region corresponding to the reflectiondisplay section 9, and the liquid crystal alignment film 3 to which therubbing treatment has been applied is formed to cover the electrodes 7and reflection film 8. The insulation film 11 is formed thinner in aregion corresponding to the transmission display section 10 than in aregion corresponding to the reflection display section 9.

[0178] As shown in FIG. 4, the electrode substrates 201 and 202 arebonded to each other by a sealing agent or the like while opposing eachother with their respective alignment films 2 and 3 inside, and theliquid crystal composition is filled in a space therebetween, wherebythe liquid crystal layer 1 is formed.

[0179] In the light display shown on the above liquid crystal display,the liquid crystal layer 1 made of the above-described liquid crystalcomposition is provided continuously across the reflection displaysection 9 and transmission display section 10. In FIG. 4, the liquidcrystal in the liquid crystal layer 1 effects the polarizationconverting function to the light passing through the liquid crystallayer 1 when aligned in parallel with the display surface as shown inthe reflection display section 9 b and transmission display section 10b, and as a consequence, for example, the dark display is shown. On theother hand, the liquid crystal in the liquid crystal layer 1 hardlyeffects the polarization converting function when alignedperpendicularly to the display surface as shown in the reflectiondisplay section 9 a and transmission display section 10 a, and as aconsequence, for example, the light display is shown.

[0180] Thus, the light display and dark display can be shown by usingthe change in the alignment in the reflection display sections 9 a and 9b and the transmission display sections 10 a and 10 b as the change inluminance of the display light by the linearly polarized light selectivetransmission function effected by the polarization plate 14 on thedisplay surface side and the polarization plate 15 on the back light 13side sandwiching the liquid crystal layer 1. In this case, as previouslymentioned, the phase difference compensation plates 16 and 17 as shownin FIG. 4 may be used to compensate the wavelength dependence of adifference of the refractive index of the liquid crystal layer 1, tochange the voltage dependence of the brightness modulated by the liquidcrystal layer 1, or to change the viewing angle characteristics, as thecase may be.

[0181] When using the optical anisotropy for the display in the abovemanner, the initial director configuration of the liquid crystal is notespecially limited, and for example, the liquid crystal layer 1 can bealigned either in parallel with or perpendicular to the display surfacewhen no voltage is applied. In the former case (aligned parallel when novoltage is applied), liquid crystal having the positive dielectricconstant anisotropy is used, while in the latter case (alignedperpendicular when no voltage is applied), liquid crystal having thenegative dielectric constant anisotropy is used.

[0182] As has been explained, the initial director configuration of theliquid crystal is not especially limited when the optical anisotropy isused for the display, but it is effective to adjust a thickness of theinsulation film 11 in such a manner as to secure a suitable thickness ofthe liquid crystal layer for the director configuration of the liquidcrystal to be used.

[0183] In order to realize the dark display in the reflection displaysection 9, light is first converted to linearly polarized light by thepolarization plate 14. Then, the polarization state is changed by thephase difference compensation plate 16 when necessary, and thepolarization state is further changed by the liquid crystal layer 1 inthe reflection display section 9 which is thinner than the transmissiondisplay section 10. Here, the necessary condition for the idea darkdisplay is to covert the polarization state on the reflection film 8 tocircularly polarized light whether right or left in the end. Also, thenecessary condition to realize the idea light display in the reflectiondisplay section 9 is to convert the polarization state on the reflectionfilm 8 to the linearly polarized light. If the director configuration ofthe liquid crystal can be controlled electrically between the darkdisplay and light display, the display states can be switched.

[0184] In other words, there must be substantially a difference of ¼wavelength (approximately 90°) between the phase difference (phasedifference of the display light on the reflection film 8) imparted tothe travelling light by the liquid crystal layer 1 before it reaches thereflection film 8 when realizing the dark display, and a phasedifference (phase difference of the display light on the reflection film8) imparted to the traveling light by the liquid crystal layer 1 beforeit reaches the reflection film 8 when realizing the light display, andthe director configuration of the liquid crystal realizing the abovecondition has to be controlled electrically, that is, the directorconfiguration of the liquid crystal has to be controlled between theones, one gives the circularly polarized light in the dark display, andthe other gives the linearly polarized light in the light display, onthe reflection film 8. Here, the linearly polarized light on thereflection film 8 to realize the light display can take any direction ofpolarization.

[0185] In the transmission display section 10, incident light isconverted to the linearly polarized light by the polarization plate 15,and its polarization state is changed by the phase differencecompensation plate 17 when necessary, and the polarization state isconverted further by the liquid crystal layer 1 formed thicker than inthe reflection display section 9. Finally, the polarization state ischanged by the phase difference compensation plate 16 when necessary,and the light exits through the polarization plate 14, whereby thedisplay is shown.

[0186] In the reflection display section 9, it is the change of thepolarization state of the light immediately before it enters thepolarization plate 14 that is used for the display. Thus, to show thelight display, the polarization state of the light immediately before itenters the polarization plate 14 is adjusted to be linearly polarizedlight having an oscillating direction along the transmission axisorientation of the polarization plate 14. On the other hand, to show thedark display, the polarization state of the light immediately before itenters the polarization plate 14 is adjusted to be linearly polarizedlight having an oscillation plane along the absorption axis orientationof the polarization plate 14.

[0187] In other words, the display can be switched if a change of thedirector configuration of the liquid crystal 1 can be controlledelectrically with the voltage application over a range such that canmake a difference of substantially ½ wavelength (approximately 180°)between the phase difference (phase difference of the display lightgoing out through the liquid crystal layer 1) imparted to the lightpassing through the liquid crystal layer 1 in the transmission displaysection 10 for the light display, and the phase difference (phasedifference of the display light going out through the liquid crystallayer 1) imparted to the light passing through the liquid crystal layer1 in the transmission display section 10 for the dark display.

[0188] The phase control of ½ wavelength means to control the polarizingorientation of the linearly polarized light immediately before it entersthe polarization plate 14 from liquid crystal layer 1, and polarizationconversion function which includes not only the control of the phasedifference caused by the retardation whose major axis of the refractiveindex is aligned uniformly parallel, but also the polarization rotationphenomenon, in which the major axis of the refractive index of theliquid crystal layer 1 is twisted along the twist of the directorconfiguration of the liquid crystal, and the polarizing orientation ofthe linearly polarized light changes in response to the twist of thedirector, which varies with the voltage. Actual polarization convertingfunction to realize the above control is the one controlling over twoorthogonal polarization states of general kind, when the application ofthe phase difference compensation plates 16 and 17 is concerned.

[0189] Examples of director configurations of the liquid crystal whichrealize the polarization converting function realizing the control ofthe polarization state (phase control of light) described above are:director configuration uniformly parallel to the substrates 4 and 5(parallel to the display surface) (homogenous alignment); directorconfiguration parallel to the substrates 4 and 5 (parallel to thedisplay surface) and twisted between the substrates 4 and 5 (an intervalbetween the substrates sandwiching the liquid crystal layer 1 above andbeneath) (twist alignment); and director configuration perpendicular tothe substrates 4 and 5 (perpendicular to the display surface)(homeotropic alignment). Further, the hybrid director configurationhaving planer alignment on one of the interfaces of the liquid crystallayer 1 and vertical alignment on the other interface and the like canbe used as well.

[0190] In case of the twist alignment, it is preferable that the liquidcrystal is twisted by an angle in a range between 60° and 100°inclusive, or 0° and 40° inclusive between the substrates 4 and 5.

[0191] This is because the conditions suitable for both the reflectiondisplay section 9 and transmission display section 10 can be satisfiedwithout changing the directions of rubbing treatment in the twosections.

[0192] To mass-produce the liquid crystal displays, the most preferableoptical design of the liquid crystal is such that monotonously increasesor decreases the display brightness (reflectance or transmittance) inresponse to a driving voltage applied to the liquid crystal layer 1between its upper and lower limits.

[0193] When the above driving conditions are concerned, the simplestoptical design of the liquid crystal layer 1 is the one such that canattain electro-optical characteristics which allow the display control,under which the display brightness monotonously increases or decreaseswhen the liquid crystal aligned substantially perpendicular to thedisplay surface is re-aligned to be substantially parallel to thedisplay surface and vice versa.

[0194] In particular, when the parallel aligning alignment film is usedto align the liquid crystal in parallel with the display surface when novoltage is applied, there are specific conditions suitable for thereflection display; on the other hand, there are specific conditionssuitable for the transmission display as well. Thus, these conditionswere computed by the Jones matrix method to find optimal twist angles.

[0195] The result of the above computation was that, to obtainsatisfactory reflection display, the twist angle must be set to a rangebetween 0° and 100° inclusive.

[0196] To be more specific, the inventors of the present inventiondiscovered that, if satisfactory reflection display is to be shown bymeans of the liquid crystal layer 1, the liquid crystal layer 1 musthave an optical property to convert the circularly polarized light tothe linearly polarized light efficiently when the liquid crystal isaligned to effect the polarization converting function (when theparallel aligning alignment film is used, the liquid crystal is alignedsubstantially in the same manner when no voltage is applied). Toevaluate the above function, the reflectance when the circularlypolarized light enters the liquid crystal layer 1 was computed by theabove-specified computation method. The reflectance computed herein isthe reflectance of the light that enters the liquid crystal cell 200 inorder of the polarization plate 14, phase difference compensation plate16 for imparting a phase difference of 90° to the light, liquid crystallayer 1, and reflection film 8, and then exits from the liquid crystalcell 200 in reversed order.

[0197] Then, it turned out that when the twist angle is in a rangebetween 0° and 70° inclusive, the circularly polarized light can beconverted to the linearly polarized light perfectly by adjusting theproduct (Δn·d) of a difference of refractive index (Δn) of the liquidcrystal in the liquid crystal layer 1 and a thickness (d) thereof foreach twist angle of the liquid crystal layer 1. Also, the inventors ofthe present invention discovered that when the twist angle is in a rangebetween 70° exclusive and 100° inclusive, although the circularlypolarized light can not be converted to the linearly polarized lightperfectly, the resulting display is satisfactorily. Thus, satisfactoryreflectance can be obtained with light having a particular wavelength byadjusting Δn·d of the liquid crystal layer 1 for each twist angle: thereflectance is 97% at the twist angle of 80°, 83% at 90°, and 72% at100°, when the maximum reflectance of the light having a visiblewavelength at the twist angle up to 70° is scaled as 100%. However, ifthe twist angle exceeds 100°, the circularly polarized light can not beconverted to the linearly polarized light because the reflectance isreduced to 54% and 37% at the twist angles of 110° and 120°,respectively. In short, it is necessary to set the twist angle of theliquid crystal layer 1 to a range between 0° and 100° inclusive in thereflection display section 9.

[0198] In the above explanation, the circularly polarized light was usedfor the computation to evaluate the polarization converting function ofthe liquid crystal layer 1 in the reflection display section 9. However,in the actual display, the incident light on the liquid crystal layer 1in the reflection display section 9 is not necessarily the circularlypolarized light, and satisfactory display can also be obtained in thereflection display section 9 if the linearly polarized light enters theabove-designed liquid crystal layer 1 instead.

[0199] On the other hand, to obtain the satisfactory display in thetransmission display section 10, the liquid crystal must be alignedeither at a small twist angle (in a range between 0° and 40° inclusive)or a large twist angle (in a range between 60° and 110° inclusive)

[0200] The polarization converting function necessary to obtainsatisfactory display in the transmission display section 10 must satisfytwo types of conditions: one is a basic optical function (firstconditions), and the other is a practical optical function (secondconditions) which is determined by a relation between the basic opticalfunction (first conditions) and the reflection display section 9.

[0201] The reason why is as follows. For example, to satisfy the firstconditions when the liquid crystal is aligned to effect the polarizationconverting function (when the parallel aligning alignment film is used,the liquid crystal is aligned substantially in the same manner when novoltage is applied), the liquid crystal layer 1 in the transmissiondisplay section 10 must efficiently convert particular polarized lightto another polarized light that is orthogonal to that particularpolarized light. To be more specific, in case that the particularpolarized light is the linearly polarized light, it is converted toanother linearly polarized light with which their respective planescontaining light oscillating electric fields intersect at right angles;in case that the particular polarized light is the circularly polarizedlight, it is converted to another circularly polarized light having aninverse rotation direction; and in case that the particular polarizedlight is elliptically polarized light in a specific state, it isconverted to another elliptically polarized light having an inverserotation direction and the same ellipticity while their major axisorientations intersecting at right angles.

[0202] Thus, the inventors of the present invention calculated thepolarization converting function by the above-specified method (Jonesmatrix method) to evaluate the above function as the indispensableproperties of the transmission display section 10, and discovered thatthe twist angle is not especially limited.

[0203] The second conditions become necessary due to a common opticalfilm (polarization plate 14 and phase difference compensation plate 16)used in both the reflection display section 9 and transmission displaysection 10 on the display front surface. The optical film on the frontsurface used both in the reflection display section 9 and transmissiondisplay section 10 is designed to show satisfactory reflection display.Another optical film set on a back surface of the display can be set tothe opposite surface of the liquid crystal display from the displaysurface, and it is preferable to provide the same at a direction suchthat realizes satisfactory display in the reflection display section 10together with the polarization plate 14 and phase differencecompensation plate 16 (serving as the optical film on the display frontsurface), and the liquid crystal layer 1 in the transmission displaysection 10 region. To do so, it is important that the polarizationconverting function of the liquid crystal layer 1 in the transmissiondisplay section 10 not only satisfies the first conditions, but alsoconverts the circularly polarized light to another circularly polarizedlight with a reversed rotation direction, or the incident linearlypolarized light to another polarized light intersecting at right angleswith the incident linearly polarized light in a satisfactory manner.

[0204] The luminance of the light, which will be converted fromcircularly polarized light to a reversed rotation direction when itpasses through the liquid crystal layer 1 in the form of circularlypolarized light, was found by the above computation method to evaluatespecific conditions satisfying the second conditions for the liquidcrystal layer 1 in the transmission display section 10. Thetransmittance computed herein is the transmittance of the light thatsequentially passes through the polarization plate 15 (serving as afirst polarization plate), phase difference compensation plate 17(serving as a first phase difference compensation plate for impartingthe phase difference of 90° to the light), liquid crystal layer 1, phasedifference compensation plate 16 (serving as a second phase differencecompensation plate having the slow axis intersecting at right angleswith a slow axis of the first phase difference compensation plate forimparting the phase difference of 90° to the light), and polarizationplate 14 (serving as a second polarization plate that intersects atright angles with the first polarization plate).

[0205] Then, the inventors of the present invention discovered thatcircularly polarized light can be converted to another circularlypolarized light with a reversed rotation direction in a satisfactorymanner when the twist angle is in a range between 0° and 40° inclusiveby adjusting Δn·d of the liquid crystal layer 1 for each twist angle.More specifically, the transmittance decreases with an increasing twistangle when the polarization converting function that converts circularlypolarized light to another circularly polarized light with an inverserotation direction is evaluated in the form of transmittance: thetransmittance at the twist angle of 30° is 88.6%, and is 80.8%, 72.0%,and 62.4% at the twist angles of 40°, 50°, and 60°, respectively, whenthe transmittance of the light having a visible wavelength at the twistangle of 0° is scaled as 100%. Consequently, the inventors of thepresent invention achieved the conclusion that it is appropriate to setthe upper limit of the twist angle at approximately 40°.

[0206] On the other hand, in setting twist angle in the transmissiondisplay section 10 which is able to efficiently convert linearlypolarized light to another linearly polarized light that intersects atthe right angles with the incident polarized light, satisfactorytransmittance can be obtained efficiently at an arbitrary twist angle of0° or above if the wavelength of the light is limited to one specificwavelength. However, to obtain high transmittance with visible light ina broad range of wavelength, the twist angle must be set to an optimalvalue. More specifically, a band-width of a wavelength range, in whichthe transmittance of 90% or above can be attained, is found by omittingthe upper and lower limits of the wavelength when Δn·d of the liquidcrystal layer 1 is adjusted by changing the twist angel in such a mannerthat the transmittance achieves the maximum of 100% at a wavelength of550 nm, which is the wavelength at the center of the visible wavelengthrange. The transmittance computed herein is the transmittance of thelight that passes through the polarization plate 15 as the firstpolarization plate, liquid crystal layer 1, and polarization plate 14 asthe second polarization plate that intersects at right angles with thefirst polarization plate, during which the liquid crystal at the centerof the liquid crystal layer 1 in its layer thickness is aligned to forman angle of 45° with respect to the transmission axes of thepolarization plates 14 and 15.

[0207] Then it turned out that the band-width (range of wavelength) is230 nm at the twist angle of 0°, 235 nm at 10°, 240 nm at 20°, 245 nm at30°, 250 nm at 40°, 255 nm at 50°, 265 nm at 60°, 280 nm at 70°, 310 nmat 80°, 330 nm at 90°, 305 nm at 100°, 255 nm at 110°, and 210 nm at120°.

[0208] In view of the foregoing, it is understood that when the twistangle is in a range between 60° and 110° inclusive, high transmittancecan be attained in a broad range of wavelength (wavelength width), andthe polarization converting function is effected in a satisfactorymanner, thereby realizing satisfactory display. Thus, the twist angle ofthe liquid crystal in the transmission display section 10 whichsatisfies the second conditions is limited to a range between 0° and 40°inclusive or a range between 60° and 110° inclusive, due to thepolarization converting function effected on circularly polarized lightor linearly polarized light.

[0209] As has been discussed, it turned out that satisfactory displaycan be obtained when the twist angle of liquid crystal layer 1 is in arange between 0° and 100° inclusive in the reflection display section 9,and in a range between 0° and 40° inclusive or in a range between 60°and 110° inclusive in the transmission display section 10.

[0210] Of all the examples explained below, when the twist angle of theliquid crystal layer 1 is equal in the reflection display section 9 andtransmission display section 10 (Examples 2 through 9 and 11), Example11 is a typical case using the circularly polarized light at the twistangle of 0° (the liquid crystal is aligned perpendicular to the displaysurface); Example 3 is a typical case using the linearly polarized lightat the twist angle of 0° (the liquid crystal display is arranged to showsatisfactory light display by using the phase difference compensationplate); and Example 5 is a typical case using the linearly polarizedlight at the twist angle of approximately 70° (the liquid crystaldisplay is arranged to show satisfactory light display by using thephase difference compensation plate).

[0211] Thus, the twist angle of the liquid crystal layer 1 to realizesatisfactory display on both the reflection display 9 and transmissiondisplay 10 is in a range between 0° and 40° inclusive or in a rangebetween 60° and 100° inclusive.

[0212] In the above explanation, the twist angle is indicated bypositive degrees. However, it should be appreciated that the sameexplanation can be applied if the twist angle is indicated by negativedegrees of the same absolute value (the twist direction is reversed inthis case).

[0213] In any case, when a small twist angle is set, a change of thepolarization state is expressed as a function of the product (Δn·d) of adifference of refractive index (Δn) and a thickness (d) of the liquidcrystal layer, and moreover, the incident light passes through theliquid crystal layer 1 and returns through the same in the reflectiondisplay section 9 while the incident light passes through the liquidcrystal layer 1 only once in the transmission display section 10.Therefore, it is preferable to make the liquid crystal layer thicker inthe transmission display section 10 than in the reflection displaysection.

[0214] It should be appreciated that normal optical rotatorypolarization used in the TN liquid crystal display can be used for thelight display and dark display exploiting the aforementionedpolarization converting function, because, in case that the TN liquidcrystal display has a thin liquid crystal layer 1, the optical rotatorypolarization and a change in the polarization state caused by theretardation can not be distinguished and elliptically polarized light isgenerally used for the display. The polarization converting function ofthe present invention includes the modulation of the luminance of thetransmitted light using the above optical rotatory polarization.

[0215] Further, as has been described above, in the above polarizationconverting function, the change of the director configuration of theliquid crystal which can change the polarization state includes: thecontrol of the director configuration of the liquid crystal to beparallel or perpendicular to the substrates 4 and 5; as in the surfacestabilized ferroelectric liquid crystal or anti-ferroelectric liquidcrystal, the change of the director direction alone while keeping thedirector direction substantially in parallel with the substrates 4 and5; and, using nematic liquid crystal, the change of the directordirection of the liquid crystal, while keeping the director direction ina plane parallel to the display surface, by changing the electrodestructure.

[0216] In the above liquid crystal display, the position (laminationorientation) of the polarization plates 14 and 15 can be set in anysuitable manner. For example, if the polarization plate 14 is set to aposition corresponding to the position of the reflection display section9, then the polarization plate 15 is set to a position corresponding tothe polarization plate 14, because the polarization plate 14 naturallyaffects the display light passing through the transmission displaysection 10 as well.

[0217] As has been explained, in case of using the non-twisted directorconfiguration of the liquid crystal, when the reflection display section9 shows, for example, the dark display, so does the transmission displaysection 10. However, for example, when only the polarization plate 15 isturned 90° while leaving the orientation of the polarization plate 14intact, the display is inverted between in the reflection displaysection 9 and in the transmission display section 10, thereby making itimpossible to obtain satisfactory display. Thus, to prevent suchunwanted inversion of the display, the polarization plate 15 is returnedto the initial position, or the electrodes are provided to thereflection display section 9 and transmission display section 10individually to invert the electrical driving itself either in thereflection display section 9 or transmission display section 10 alone,so that both the display sections shows either the light or dark displaysimultaneously.

[0218] Next, the display principle in the reflection display section 9and transmission display section 10 of the liquid crystal display ofFIG. 4 will be explained in further detail.

[0219] To begin with, the display principle in the reflection displaysection 9 will be explained. Assume, for ease of explanation, that thephase difference compensation plates 16 and 17 are omitted and thedirector configuration of the liquid crystal in the liquid crystal layer1 is not twisted in the reflection display section 9 b nor transmissiondisplay section 10 b. Also, assume that the thicknesses of the liquidcrystal layer 1 in the reflection display section 9 and transmissiondisplay section 10 are adjusted in such a manner that the reflectiondisplay section 9 b and transmission display section 10 b respectivelycause phase differences of ¼ wavelength and ½ wavelength when the lighthaving a wavelength of 550 nm passes through the liquid crystal layer 1only once. Also, the liquid crystal composition has positive dielectricconstant anisotropy and the liquid crystal is aligned substantially inparallel with the substrates 4 and 5 when no voltage is applied, and thealignment orientation and the absorption axis orientation of thepolarization plate 14 form 45° within display plane.

[0220] In this case, the director configuration of the liquid crystal inthe reflection display section 9 and transmission display section 10when no voltage is applied is the director configuration of the liquidcrystal shown in the reflection display section 9 b and transmissiondisplay section 10 b, and upon application of a voltage, the directorconfiguration of the liquid crystal in the reflection display section 9and transmission display section 10 is changed to the one shown in thereflection display section 9 a and transmission display section 10 a.

[0221] In the reflection display section 9 b, the product (Δn·d) of adifference of refractive index (Δn) of the liquid crystal compositionand a thickness (d) of the liquid crystal layer satisfies the ¼wavelength condition. Thus, the ambient light is converted to linearlypolarized light by the polarization plate 14 when it enters the liquidcrystal layer 1, and converted further to circularly polarized light bythe retardation of the liquid crystal layer 1 before it reaches thereflection film 8. The incident light inverts its direction ofpropagation on the reflection film 8, while the circularly polarizedlight inverts its direction of propagation alone while keeping therotational direction of the oscillating electric field. Hence, thecircularly polarized light is converted to circularly polarized lightorthogonal to the polarized light at the time of incidence, in otherwords, circularly polarized light is inverted from right to left. Then,the resulting circularly polarized light is converted to linearlypolarized light parallel to the absorption axis orientation of thepolarization plate 14 after it has passed through the liquid crystallayer 1 in the reflection display section 9 b again, and absorbed by thepolarization plate 14, thereby showing the dark display.

[0222] Here, in the transmission display section 10 b, the product(Δn·d) of a difference of refractive index (Δn) of the liquid crystalcomposition and a thickness (d) of the liquid crystal layer satisfiesthe ½ wavelength condition. Thus, the liquid crystal layer 1 has afunction of converting the orientation of the oscillation plane of thelinearly polarized incident light symmetrically with respect to a linealong the alignment direction of the liquid crystal. Thus, theorientation of the absorption axis of the polarization plate 15 on thelight incident side in the transmission display section 10 b isdetermined to become parallel to the transmission axis orientation ofthe polarization plates 14 and 15, so that the light passing through thepolarization plate 14 is absorbed therein by the aforementioned functionof the liquid crystal layer 1, thereby showing the dark display.

[0223] As mentioned above, it has been discovered that, when thepolarization plates 14 and 15 are provided in such a manner that theirtransmission axis orientations are parallel to each other, and thealignment direction of the liquid crystal and the transmission axisorientation forms angle of 45° in the above manner, both the reflectiondisplay section 9 b and transmission display section 10 b show the darkdisplay.

[0224] Next, the following will explain a function when the directorconfiguration of the liquid crystal is changed to be substantiallyperpendicular to the display surface as shown in the reflection displaysection 9 a and transmission display section 10 a by supplying apotential difference between the electrodes 6 and 7 from the state whereno voltage is applied (initial director configuration of the liquidcrystal) as shown in the reflection display section 9 b and transmissiondisplay section 10 b.

[0225] In this case, in the reflection display section 9 a, the ambientlight is converted to linearly polarized light by the polarization plate14, and since the liquid crystal layer 1 does not have the retardationfor the linearly polarized light, the incident light reaches thereflection film 8 while maintaining its polarization state. After thedirection of propagation is inverted, the light passes through theliquid crystal layer 1 again, and exits through the polarization plate14 while maintaining its direction of polarization which intersect atright angles with the absorption axis orientation of the polarizationplate 14.

[0226] Also, like in the reflection display section 9 a, in thetransmission display section 10 a, the incident light is converted tolinearly polarized light by the polarization plate 15, and passesthrough the polarization plate 14 while keeping its polarization statesubstantially the same.

[0227] When using the above polarization converting function exploitingthe optical anisotropy for the display, an amount of the polarizationconverting function is determined, for example, when the liquid crystalis aligned in parallel with the display surface and no voltage isapplied to the liquid crystal layer 1, by an angle of twist of thedirector configuration of the liquid crystal layer 1, and the product(Δn·d) of a thickness (d) of the liquid crystal layer and a differenceof refractive index (Δn) of the liquid crystal composition. Thus,providing a thicker liquid crystal layer in the transmission displaysection 10 than in the reflection display section 9, as in the presentinvention, is effective for a liquid crystal display using both thetransmitted light and reflected light for the display to obtainsatisfactory brightness and contrast ratio for the display in both thereflection display section 9 and transmission display section 10. Theangle of twist may be different in the reflection display section 9 andtransmission display section 10.

[0228] When the liquid crystal display includes the phase differencecompensation plates 16 and 17, satisfactory brightness and contrastratio can be attained in a reliable manner with respect to light havingmore than one wavelength in the range of visible light, thereby makingit possible to realize even more satisfactory display.

[0229] Also, if the liquid crystal composition and directorconfiguration of the liquid crystal layer 1 are identical to one in theabove explanation, a change in the display can be inverted by thefunction of the phase difference compensation plates 16 and 17. Morespecifically, when ¼ wavelength plates are used as the phase differencecompensation plates 16 and 17, in the reflection display section 9 b,the ambient light is converted to circularly polarized light by thephase difference compensation plate 16 upon incidence on the liquidcrystal layer 1, and converted further to linearly polarized light bythe polarization converting function exploiting the optical anisotropyof the liquid crystal layer 1 before it reaches the reflection film 8.Then, after its direction of propagation is inverted at the reflectionfilm 8, the linearly polarized light becomes the transmission componentsof the polarization plate 14 and exits through the same, thereby showingthe light display. On the other hand, when the director configuration ofthe liquid crystal is changed as shown in the reflection display section9 a, the ambient light reaches the reflection film 8 as the circularlypolarized light, thereby showing the dark display.

[0230] The foregoing explained a case where the dark display changes tothe light display with an increasing potential difference between theelectrodes 6 and 7 was explained. However, it should be a appreciatedsuch a change in display is not limited to the above disclosure. Forexample, as has been explained, the display can be inverted by using aliquid crystal composition having negative dielectric constantanisotropy in the liquid crystal layer 1, or giving the liquid crystalvertical alignment in the initial stage.

[0231] Here, setting the initial director configuration of the liquidcrystal perpendicular to the display surface can offer technicalcharacteristics such that the polarization converting function of theinitial director configuration is not greatly affected by amanufacturing accuracy of the thickness of the liquid crystal layer.Thus, taking advantage of the above characteristics it is highlyproductive to assign the initial director configuration to blackdisplay, thereby stabilizing black display, which affects displayquality considerably. In particular, to do so, black must be shown at astate where the polarization converting function of the perpendicularlyaligned liquid crystal layer 1 is almost completely lost, and the phasedifference compensation plate 16 must have satisfactory circularlypolarizing function. In short, it is important that the phase differencecompensation plate 16 is arranged in such a manner as to convert theincident light to circularly polarized light in a wavelength range asbroad as possible.

[0232] When the phase difference compensation plates 16 and 17 areprovided to have their respective slow axis orientations intersecting atright angles and the polarization plates 14 and 15 are provided to havetheir respective absorption axis orientations intersecting at rightangles, the transmission display section 10 shows the light display withthe director configuration of the liquid crystal shown in thetransmission display section 10 b and the dark display with the directorconfiguration of the liquid crystal shown in the transmission displaysection 10 a.

[0233] In the liquid crystal display of the present invention, whetherthe liquid crystal layer 1 is aligned in parallel with or perpendicularto the display surface, in case that the thicknesses of the liquidcrystal layer are different in the reflection display section 9 andtransmission display section 10, to obtain satisfactory brightness andcontrast ratio both in the reflection display section 9 and transmissiondisplay section 10, when the reflection display section 9 shows thedisplay by letting the incident light from the display surface side passthrough the liquid crystal layer 1 and go out to the display surfaceside through the liquid crystal layer 1 again, and the transmissiondisplay section 10 shows the display by letting the incident light frombehind (back light 13 side) pass through the liquid crystal layer 1 onlyonce and go out to the display surface side, it is very effective tomake the liquid crystal layer thicker in the transmission displaysection 10 than in the reflection display section 9, and therefore, tosatisfy the aforementioned conditions.

[0234] In the following, of all the liquid crystal displays of thepresent embodiment, those using the change of the polarization statecaused by the polarization converting function of the liquid crystallayer 1 with the polarization plates 14 and 15 will be explained by wayof examples and comparative examples with reference to FIGS. 4 through 8for purposes of explanation only, without any intention as a definitionof the limits of the invention.

EXAMPLES 2-4

[0235] In each of Examples 2 through 4, liquid crystal cells for fillingare assembled in the same manner as Example 1. Here, the thicknesses (d)of the liquid crystal layer in the transmission display section 10 andreflection display section 9 are 7.5 μm and 4.5 μm, respectively. Inother words, in Examples 2 through 4, the liquid crystal layer 1 is madethicker in the transmission display section 10 than in the reflectiondisplay section 9 by patterning the insulation film 11 in such a manneras to leave no photosensitive resin in the transmission display section10 and form a 3 μm-thick layer of the photosensitive resin in thereflection display section 9. However, in Examples 2 through 4, as shownin FIG. 4, the electrode pattern is formed in such a manner that theelectrode 7 of the reflection display section 9 and the electrode 7 ofthe transmission display section 10 are electrically isolated, so that avoltage is applied to each separately from outside the liquid crystalcell.

[0236] Further, in Examples 2 through 4, the liquid crystal layer 1 isproduced by filling liquid crystal composition with no chiral dopant,having positive dielectric constant anisotropy and a difference ofrefractive index (Δn) of 0.065 by means of vacuum injection.

[0237] Then, the liquid crystal displays are assembled by laminating thephase difference compensation plates 16 and 17 and polarization plates14 and 15 to the outside of the respective electrode substrates of theliquid crystal cell produced in the above manner. Here, the phasedifference compensation plate 17 is composed of two phase differencecompensation plates in Examples 2 through 4, while the phase differencecompensation plate 16 is composed of two phase difference compensationplates in Examples 2 and 4, and a single phase difference compensationplate in Example 3. The lamination orientation of the phase differencecompensation plates 16 and 17 and polarization plates 14 and 15 isdetermined correspondingly to the alignment direction (alignmentorientation) of the liquid crystal.

[0238] In Example 2, homogeneous alignment is used as the directorconfiguration of the liquid crystal, and the NB (Normally Black) mode isused for the display mode. In Example 3, the homogenous alignment isused as the director configuration of the liquid crystal, and the NW(Normally White) mode is used for the display mode. In Example 4, acombination of these modes are used (the NB mode is used for thereflection display, and the NW mode is used for the transmissiondisplay).

[0239] In Examples 2 through 4, parallel aligning alignment films areused as the alignment films 2 and 3, so that the liquid crystal isaligned in parallel with the display surface when no voltage is appliedto the liquid crystal layer 1, and the alignment treatment is applied tothese alignment films 2 and 3 to form a crossed rubbing angle of 180°.

[0240] Here, the crossed rubbing angle is defined, as shown in FIG. 5,in the liquid crystal cell for filling composed of a pair of electrodesubstrates sandwiching the liquid crystal layer 1, as an angle of therubbing direction Y of the alignment treatment orientation of thealignment film 3 (the alignment film 3 on the substrate 5 side) on theelectrode substrate in a let direction with respect to the rubbingdirection X of the alignment treatment orientation of the otheralignment film 2 (alignment film 2 on the substrate 4 side) on theelectrode substrate on the viewer's side.

[0241] The director configuration of the liquid crystal molecules in theliquid crystal layer 1 sandwiched by the alignment treated alignmentfilms 2 and 3 is determined by the alignment properties of the alignmentfilms 2 and 3, a concentration of the chiral dopant for imparting anatural twist to the liquid crystal, and the crossed rubbing angle, whenneither electric field nor magnetic field exists.

[0242] When the crossed rubbing angle is 180°, the liquid crystalcomposition aligns itself without twisting when no chiral dopant isadded. When the chiral dopant induces a left-handed twist, the directorconfiguration of the liquid crystal remains intact until a predeterminedamount of the chiral dopant is added, and when an amount added exceedsthe predetermined amount, the liquid crystal twists 180° to the left(180° left twist alignment), and with a further increasing amount of thechiral dopant, the liquid crystal twists by an angle of an integralmultiple of 180°.

[0243] Thus, in the present embodiment, given x° as the rubbingorientation X of the alignment film 2 provided on the electrodesubstrate above the liquid crystal layer 1, then the alignmentorientation of the liquid crystal on the alignment film 3 realized bythe crossed rubbing angle (180°) is x° when no chiral dopant is added,and the alignment orientation is (180°+x) when the liquid crystal istwisted 180° to the left between the electrode substrates above andbeneath the liquid crystal layer 1 with an increasing amount of thechiral dopant.

[0244] In case that the nematic liquid crystal having positivedielectric constant anisotropy and no chiral dopant is used when thealignment films 2 and 3 are the parallel aligning alignment films thatalign the liquid crystal in parallel with their film surfaces, when novoltage is applied, the liquid crystal molecules take an directorconfiguration substantially parallel to the electrode substratessandwiching the liquid crystal layer 1 above and beneath with no twist(that is, the homogenous alignment), and upon voltage application, thealignment starts to change from the central portion of the liquidcrystal layer 1 in the layer thickness direction.

[0245] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the liquid crystaldisplays in Examples 2 through 4 is set forth in Table 1 below for readycomparison with reference to a common orientation in any example.

[0246] The optical set forth in Table 1 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and when the phase difference compensation plate 16 or 17 iscomposed of more than one phase difference compensation plate, eachphase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side.

[0247] Since the liquid crystal layer 1 is aligned without any twist,the alignment orientation (alignment orientation of the major axis ofthe liquid crystal molecules) of the entire liquid crystal layer 1 whenno voltage is applied is set forth in Table 1 below, and this alignmentorientation is the orientation of the rubbing treatment applied to thealignment film 2 on the substrate 4 side.

[0248] Each orientation is expressed in degrees from the referenceorientation set arbitrarily on the display surface, and the retardation(product of a difference of in-plane refractive index and a thickness ofthe phase difference compensation plate) of each phase differencecompensation plate is expressed in nm with respect to a beam ofmonochrome light having the wavelength of 550 nm. TABLE 1 EXAMPLE 2 3 4PLATE 14 TRANSMISSION AXIS 0 0 0 ORIENTATION (°) PLATE PLATE SLOW AXISORIENTATION 15 15 15 16 (°) RETARDATION (nm) 270 270 270 PLATE SLOW AXIS165 — 165 ORIENTATION (°) RETARDATION (nm) 135 — 135 LC LAYER 1ALIGNMENT ORIENTATION 75 75 75 (°) PLATE PLATE SLOW AXIS 165 165 165 17ORIENTATION (°) RETARDATION (nm) 70 220 90 PLATE SLOW AXIS 135 135 105ORIENTATION (°) RETARDATION (nm) 270 270 270 PLATE 15 TRANSMISSION AXIS60 60 90 ORIENTATION (°)

[0249] The display characteristics of the liquid crystal displaysassembled in Examples 2 through 4 are graphed in FIGS. 6 through 8,respectively. These display characteristics were measured in the samemanner as Example 1, and in these drawings, the horizontal axisrepresents a root mean square value of the applied voltage, and thevertical axis represents the brightness (reflectance or transmittance).Here, the transmittance of the transmission display section 10 when thepolarization plates 14 and 15 are not provided is scaled as 100%, andthe reflectance of the reflection display section 9 before thepolarization plate 14 is provided is scaled as 100%.

[0250] In FIG. 6, a curve 211 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 212 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 2.

[0251]FIG. 6 reveals that, in Example 2, while the applied voltage is ina range between 1V and 2V, both the reflectance and transmittanceincrease with an increasing applied voltage. That is, when the appliedvoltage is 1V, the reflectance of the reflection display section 9 andthe transmittance of the transmission display section 10 are 3% and 2%,respectively, and when the applied voltage is increased to 2V, bothincrease to 40%.

[0252] In FIG. 7, a curve 221 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 222 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 3.

[0253]FIG. 7 reveals that, in Example 3, while the applied voltage is ina range between 1V and 2V, both the reflection and transmittancedecrease with an increasing applied voltage. That is, when the appliedvoltage is 1V, both the reflectance of the reflection display section 9and the transmittance of the transmission display section 10 are 40%,and when the applied voltage is increased to 2V, both decrease to 3% and2%, respectively.

[0254] In FIG. 8, a curve 231 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 232 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 4.

[0255]FIG. 8 reveals that, in Example 4, while the applied voltage is ina range between 1V and 2V, the reflectance increases while thetransmittance decreases with an increasing applied voltage. That is,when the applied voltage is 1V, the reflectance of the reflectiondisplay section 9 and the transmittance of the transmission displaysection 10 are 3% and 40%, respectively, and when the applied voltage isincreased to 2V, the reflectance of the reflection display section 9increases to 40%, while the transmittance of the transmission displaysection 10 decreases to 2%.

[0256] As has been explained, in all the liquid crystal displaysassembled in Examples 2 through 4, the transmittance and reflectancechange in response to a change in the applied voltage, and each can showboth the reflection display and transmission display.

[0257] Further, the changes were checked visually. Then, in Examples 2and 3, it was confirmed that the changes between the light display anddark display is equal and the display was not inverted (from light todark and vice versa) in the reflection display section 9 andtransmission display section 10. This is because the display is shown byapplying the same voltage to the electrode 7 of the reflection displaysection 9 and the electrode 7 of the transmission display section 10 tokeep the applied voltage to the liquid crystal layer 1 equal in thereflection display section 9 and transmission display section 10 bymeans of the electrodes 6 and 7. In addition, no change in the contentof the display was observed when the luminance of the ambient light waschanged during the observation. In other words, when the reflectiondisplay section 9 shows the dark display, so does the transmissiondisplay section 10, and when the reflection display section 9 shows thelight display, so does the transmission display section 10. For thisreason, even when the reflection display section 9 and transmissiondisplay section 10 are driven by the same electrode 7 as is shown inFIG. 1, the display is not inverted.

[0258] By contrast, in Example 4, when the voltage is applied in thesame manner as Examples 2 and 3, that is, when a voltage of 1V isapplied, the transmission display section 10 shows the light displaywhile the reflection display section 9 shows the dark display. Then,when a voltage of 2V is applied, the transmission display section 10shows the dark display while the reflection display section 9 shows thelight display. Hence, the displays are inverted in the reflectiondisplay section 9 and transmission display section 10. Thus, when thedisplay is shown under the circumstance where the ambient light is weak,and the display is shown by the reflection display by brightening theambient light when the user is mainly observing the transmission displaysection 10, the display is inverted (from light to dark and vice versa),and as a consequence, it becomes difficult to see the display content.Thus, when, as in Example 4, the same voltage was applied to theelectrode 7 in the reflection display section 9 and the electrode 7 inthe transmission display section 10, it was confirmed that the displaysof the reflection display section 9 and transmission display section 10were inverted considerably in a combination mode of the NB and NW,thereby deteriorating the visibility.

[0259] However, in Example 4, the problem of such unwanted inversion ofthe dark display and light display can be resolved and a display stateas satisfactory as those in Examples 2 and 3 can be obtained by applyingdifferent voltages to the electrode 7 in the reflection display section9 and the electrode 7 in the transmission display section 10, so thatwhen the reflection display section 9 shows the light display, so doesthe transmission display section 10, and when the reflection displaysection 9 shows the dark display, so does the transmission displaysection 10. More specifically, by means of the electrodes 6 and 7(alignment mechanism), when a voltage of 1V is applied to the reflectiondisplay section 9 to let the same show the dark display, a voltage of 2Vis applied to the transmission display section 10 to let the same showthe dark display too, but when a voltage of 2V is applied to thereflection display section 9 to let the same show the light display, avoltage of 1V is applied to the transmission display section 10 to letthe same show the light display too.

[0260] In view of the foregoing, the liquid crystal display in any ofExamples 2 through 4 can attain satisfactory brightness and contrastratio for the light display in both the reflection display section 9 andtransmission display section 10. Moreover, the liquid crystal display inany of Examples 2 through 4 can match the dark/light display in thereflection display section 9 and transmission display section 10,thereby realizing display with excellent visibility. Further, the liquidcrystal display in any of Examples 2 through 4 has a higher contrastratio in the transmission display section 10 than in the reflectiondisplay section 9. Consequently, the display quality can be furtherimproved and more satisfactory display can be shown.

[0261] Next, of all the liquid crystal displays of the presentembodiment, a liquid crystal display using the polarization convertingfunction of the liquid crystal layer 1 effected by the twist alignmentthereof will be explained by way of examples and comparative exampleswith reference to FIGS. 9 and 10 for purposes of explanation only,without any intention as a definition of the limits of the invention.

EXAMPLE 5

[0262] In the present example, a liquid crystal cell for filling isassembled in the same manner as Example 1. Here, the thicknesses (d) ofthe liquid crystal layer in the transmission display section 10 andreflection display section 9 are 7.5 μm and 4.5 μm, respectively. Inother words, in the present example too, the thickness of the liquidcrystal layer is made thicker in the transmission display section 10than in the reflection display section 9 by patterning the insulationfilm 11 in such a manner as to leave no photosensitive resin in thetransmission display section 10 and form a 3 μm-thick layer of thephotosensitive resin in the reflection display section 9.

[0263] However, in the present example, like in Examples 2 through 4 asshown in FIG. 4, the electrode pattern is formed in such a manner thatthe electrode 7 of the reflection display section 9 and the electrode 7of the transmission display section 10 are electrically isolated, sothat a voltage is applied to each separately from outside the liquidcrystal cell.

[0264] Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,the phase difference compensation plate 17 is composed of a single phasedifference compensation plate, while the phase difference compensationplate 16 is composed of two phase difference compensation plates. Thelamination orientation of the phase difference compensation plates 16and 17 and polarization plates 14 and 15 is determined correspondinglyto the alignment direction (alignment orientation) of the liquidcrystal.

[0265] In the present example, the liquid crystal display is assembledin such a manner that the twist director configuration of the liquidcrystal layer 1 (angle of twist of the director configuration of theliquid crystal (twist angle)) is 70°. More specifically, parallelaligning alignment films are used as the alignment films 2 and 3, sothat the director configuration of the liquid crystal is parallel to thedisplay surface when no voltage is applied, and the alignment treatmentis applied to these alignment films 2 and 3 by means of rubbing in sucha manner as to form the crossed rubbing angle of 250°. The crossedrubbing angle is defined as above. Then, the liquid crystal layer 1 isproduced by using vacuum injection to full a space between the electrodesubstrates of the above liquid crystal cell with a liquid crystalcomposition having a difference of refractive index (Δn) of 0.065 andpositive dielectric constant anisotropy. The above alignment treatmentand the function of the chiral dopant added to the liquid crystalcomposition impart an angle of twist (twist angle) of 70° to thedirector configuration of the liquid crystal. The liquid crystal layer 1aligned in this manner starts to change its alignment upon applicationof the voltage from the central portion thereof in the layer thicknessdirection.

[0266] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the liquid crystaldisplay of the present example is set forth in Table 2 below for readycomparison with reference to a common orientation.

EXAMPLE 6

[0267] In the present example, like in Example 5, a liquid crystal cellfor filling is assembled in the same manner as Example 1. Here, thethicknesses (d) of the liquid crystal layer in the transmission displaysection 10 and reflection display section 9 are 7.5 μm and 4.5 μm,respectively. Also, as shown in FIG. 4, the electrode pattern is formedin such a manner that the electrode 7 of the reflection display section9 and the electrode 7 of the transmission display section 10 areelectrically isolated, so that a voltage is applied to each separatelyfrom outside the liquid crystal cell.

[0268] Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof a single phase difference compensation plate. The laminationorientation of the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 is determined correspondingly to thealignment direction (alignment orientation) of the liquid crystal.

[0269] In the present example, the liquid crystal display is assembledin such a manner that the twist director configuration of the liquidcrystal layer 1 (twist angle) is 90°. More specifically, parallelaligning alignment films are used as the alignment films 2 and 3, sothat the director configuration of the liquid crystal becomes parallelto the display surface when no voltage is applied, and the alignmenttreatment is applied to these alignment films 2 and 3 by means ofrubbing in such a manner as to form the crossed rubbing angle of 270°.The crossed rubbing angle is defined as above. Then, the liquid crystallayer 1 is produced by filling the liquid crystal composition having adifference of refractive index (Δn) of 0.065 and the positive dielectricconstant anisotropy into a space between the electrode substrates of theliquid crystal cell for filling by means of vacuum injection. The abovealignment treatment and the function of the chiral dopant added to theliquid crystal composition impart the angle of twist (twist angle) of90° to the director configuration of the liquid crystal. The liquidcrystal layer 1 aligned in this manner starts to change its alignmentupon application of the voltage from the central portion thereof in thelayer thickness direction.

[0270] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the liquid crystaldisplay of the present example is set forth in Table 2 below for readycomparison with a reference to common orientation.

[0271] The optical set forth in Table 2 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and when the phase difference compensation plate 16 or 17 iscomposed of more than one phase difference compensation plate, eachphase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side.

[0272] The alignment orientation of the liquid crystal layer 1 (thealignment orientation of the major axis of the liquid crystal molecules)on the substrate 4 side is identical with the orientation of the rubbingtreatment applied to the alignment film 2 on the substrate 4, and on thesubstrate 5 side is identical with the orientation of the rubbingtreatment applied to the alignment film 3 on the substrate 5. Note that,however, when the alignment orientation of the liquid crystal touchingthe alignment film 2 is traced toward the alignment film 3, thealignment orientation is twisted 90° to the left. In case that thedirector configuration of the liquid crystal is traced in the abovemanner, on the assumption that the orientation of the rubbing treatmentapplied to the alignment film 2 is the alignment orientation on thesubstrate 4 side (hereinafter, referred to as the substrate 4 alignmentorientation), the rubbing orientation of the alignment film 3 isinverted by 180° from the orientation traced along the twist of thedirector configuration of the liquid crystal. In the following, thealignment orientation on the substrate 5 side (hereinafter, referred toas the substrate 5 alignment orientation) is defined as the directorconfiguration of the liquid crystal on the substrate 5 traced along thetwist of the director configuration of the liquid crystal from thesubstrate 4 alignment orientation.

[0273] Each orientation is expressed in degrees from the referenceorientation set arbitrarily on the display surface, and the retardationof each phase difference compensation plate is expressed in nm withrespect to a beam of monochrome light having the wavelength of 550 nm.TABLE 2 EXAMPLE 5 6 PLATE 14 TRANSMISSION AXIS ORIENTA- 0 0 TION (°)PLATE PLATE SLOW AXIS ORIENTATION (°) 18 12 16 RETARDATION (nm) 270 135PLATE SLOW AXIS ORIENTATION (°) 126 — RETARDATION (nm) 135 — LC LAYER 1SUBSTRATE 4 ALIGNMENT 16 −11 ORIENTATION (°) SUBSTRATE 5 ALIGNMENT 86 79ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION (°) −4 135 17RETARDATION (nm) 260 260 PLATE 15 TRANSMISSION AXIS ORIENTA- 152 90 TION(°)

[0274] The display characteristics of the liquid crystal displaysassembled in Examples 5 and 6 are graphed in FIGS. 9 and 10,respectively. These display characteristics were measured in the samemanner as Example 1, and in each drawing, the horizontal axis representsa root mean square value of the applied voltage, and the vertical axisrepresents the brightness (reflectance or transmittance). Here, thetransmittance of the transmission display section 10 when thepolarization plates 14 and 15 are not provided is scaled as 100%, andthe reflectance of the reflection display section 9 before thepolarization plate 14 is provided is scaled as 100%.

[0275] In FIG. 9, a curve 241 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 242 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 5.

[0276]FIG. 9 reveals that, in Example 5, while the applied voltage is1.2V or higher, both the reflectance and transmittance increase with anincreasing applied voltage. That is, when the applied voltage is 1V, thereflectance of the reflection display section 9 and the transmittance ofthe transmission display section 10 are 3% and 2%, respectively, andwhen the applied voltage is increased to 4V, both increase to 41% and40%, respectively.

[0277] In FIG. 10, a curve 251 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 252 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 6.

[0278]FIG. 10 reveals that, in Example 6, like in Example 5, while theapplied voltage is 1.2V or higher, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 2%, respectively, and when the applied voltage is increasedto 4V, both increase to 35% and 37%, respectively.

[0279] As has been explained, in each of the liquid crystal displaysassembled in Examples 5 and 6, the transmittance and reflectance changein response to a change in the applied voltage, and each can show boththe reflection display and transmission display.

[0280] Further, the changes were checked visually. Then, in Examples 5and 6, it was confirmed that the changes between the light display anddark display were equal and the display was not inverted (from light todark and vice versa) in the reflection display section 9 andtransmission display section 10, even when the display is shown byapplying the same voltage to the electrode 7 of the reflection displaysection 9 and the electrode 7 of the transmission display section 10 tokeep the applied voltage to the liquid crystal layer 1 equal in thereflection display section 9 and transmission display section 10 by theelectrodes 6 and 7. In addition, a change in the content of the displayis not observed when the luminance of the ambient light is changedduring the observation. In other words, when the reflection displaysection 9 shows the dark display, so does the transmission displaysection 10, and when the reflection display section 9 shows the lightdisplay, so does the transmission display section 10. For this reason,even when the reflection display section 9 and transmission displaysection 10 are driven by the same electrode 7 as is shown in FIG. 1, thedisplay is not inverted in Example 5 nor 6.

[0281] In view of the foregoing, the liquid crystal displays in Examples5 and 6 can attain satisfactory brightness and contrast ratio for thelight display in both the reflection display section 9 and transmissiondisplay section 10. Moreover, the liquid crystal displays in Examples 5and 6 can match the dark/light display in the reflection display section9 and transmission display section 10, thereby realizing display withexcellent visibility. Further, the liquid crystal displays in Examples 5and 6 have a higher contrast ratio in the transmission display section10 than in the reflection display section 9. Consequently, the displayquality can be further improved and more satisfactory display can beshown.

[0282] Also, both the liquid crystal displays of Examples 5 and 6 havegood visibility, and can show a high-resolution color display whileusing both the reflected light and transmitted light, but the liquidcrystal display of Example 6 is less expensive compared with itscounterpart of Example 5, because the former uses fewer phase differencecompensation plates.

[0283] Explained in the present embodiment was the liquid crystaldisplay which can show satisfactory reflection display and transmissiondisplay by changing the thickness of the liquid crystal layer in thereflection display section and transmission display section. Thefollowing will explain a liquid crystal display, which can showsatisfactory reflection display and transmission display even though thethicknesses of the liquid crystal layer in the reflection displaysection and transmission display section are equal.

Embodiment 3

[0284] Explained in the present embodiment is a liquid crystal displaywhich has the equal thickness of the liquid crystal layer in thereflection display section and transmission display section but can showsatisfactory reflection display and transmission display by changing thedirector configuration of the liquid crystal by applying differentvoltages to the reflection display section and transmission displaysection.

[0285] In the present embodiment, a liquid crystal display, which hasthe polarization plates 14 and 15 of Embodiment 2 and the equalthickness of the liquid crystal layer in the reflection display sectionand transmission display section and uses the retardation of the liquidcrystal layer 1 for the display, will be explained by way of examplesand comparative examples with reference to FIGS. 4 and 11 through 16 forpurposes of explanation only, without any intention as a definition ofthe limits of the invention.

[0286] Hereinafter, like components are labeled with like referencenumerals with respect to Embodiments 1 and 2, and, for ease ofexplanation, the description of these components is not repeated here.Also, the arrangement of the entire liquid crystal display of thepresent embodiment is identical with its counterpart of Embodiment 2except that the thickness of the liquid crystal layer is equal in thereflection display section 9 and transmission display section 10, andthe description of which is not repeated either for ease of explanation.

[0287] To give the liquid crystal layer 1 equal thicknesses in thereflection display section 9 and transmission display section 10 like inthe present embodiment, the insulation film 11 is omitted and theelectrode 7 is formed directly on the substrate 5, for example.

EXAMPLE 7

[0288] In the present example, a liquid crystal cell for filling, havingthe liquid crystal layer having a thickness (d) of 4.5 μm both in thereflection display section 9 and transmission display section 10 isproduced in the same manner as Example 1 except that the insulation film11 made of the insulation photosensitive resin is not formed on thesubstrate 5, and that, as shown in FIG. 4, the electrode pattern isformed in such a manner that the electrode 7 of the reflection displaysection 9 and the electrode 7 of the transmission display section 10 areelectrically isolated, so that a voltage is applied to each separatelyfrom outside the liquid crystal cell.

[0289] Then, the liquid crystal layer 1 is produced by filling theliquid crystal composition having a difference of refractive index (Δn)of 0.065 and positive dielectric constant anisotropy into the liquidcrystal cell for filling by means of vacuum injection.

[0290] Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates. The lamination orientationof the phase difference compensation plates 16 and 17 and polarizationplates 14 and 15 is determined correspondingly to the alignmentdirection (alignment orientation) of the liquid crystal.

[0291] In the present example, the liquid crystal in the liquid crystallayer 1 is aligned in parallel with the substrates 4 and 5 (parallel tothe display surface) with no twist, and the birefringence mode using theretardation of the liquid crystal layer 1 for the display is adopted asthe liquid crystal display method.

[0292] Also, in the present example, the retardation suitable for thereflection display is used for the transmission display section 10.Here, the reflection display section 9 is arranged in the same manner asits counterpart of Example 2 in Embodiment 2, while the transmissiondisplay section 10 is arranged differently from its counterpart ofExample 2 in that it has the liquid crystal layer as thick as the one inthe reflection display section 9. Thus, to assemble the liquid crystaldisplay of the present example, the liquid crystal display of Example 2is re-designed optically to determine the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17. Inthe present example, the optical of the polarization plates 14 and 15and phase difference compensation plates 16 and 17 is determined in sucha manner that the transmission display section 10 can show satisfactorydark display.

[0293] In the present example, like in Example 2, parallel aligningalignment films are used as the alignment films 2 and 3 to align theliquid crystal in parallel with the display surface when no voltage isapplied to the liquid crystal layer 1, and the alignment treatment isapplied to these alignment films 2 and 3 in such a manner as to form thecrossed rubbing angle of 180°.

[0294] In the above alignment treatment, the angle of twist of thedirector configuration of the liquid crystal (twist angle) is 0°, andthe alignment starts to change upon the voltage application from thecentral portion of the liquid crystal in the layer thickness directionof the liquid crystal layer 1.

[0295] The optical of the polarization plates 14 and 15, phasedifference compensation plates 14 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the liquid crystaldisplay of the present example is set forth in Table 3 below for readycomparison with reference to a common orientation.

COMPARATIVE EXAMPLE 3

[0296] In the present comparative example with respect to Example 7above, a comparative liquid crystal display is assembled in the samemanner as Example 7 except that the phase difference compensation plate16 is composed of two phase difference compensation plates while thephase difference compensation plate 17 is composed of a single phasedifference compensation plate, and that the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17 isset in such a manner that the transmission display section 10 can showsatisfactory light display. The lamination orientation of the phasedifference compensation plates 16 and 17 and polarization plates 14 and15 is determined correspondingly to the alignment direction (alignmentorientation) of the liquid crystal.

[0297] In the present comparative example, like in Example 7, parallelaligning alignment films are used as the alignment films 2 and 3 toalign the liquid crystal in parallel with the display surface when novoltage is applied to the liquid crystal layer 1, and the alignmenttreatment is applied to these alignment films 2 and 3 in such a manneras to form the crossed rubbing angle of 180°.

[0298] In the above alignment treatment, the angle of twist of thedirector configuration of the liquid crystal (twist angle) is 0°, andthe alignment starts to change upon the voltage application from thecentral portion of the liquid crystal in the layer thickness directionof the liquid crystal layer 1.

[0299] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the comparative liquidcrystal display of the present comparative example is set forth in Table3 below for ready comparison with reference to a common orientation.

EXAMPLE 8

[0300] A liquid crystal display of the present example is assembled inthe same manner as Example 7 except that the thickness (d) of the liquidcrystal layer in both the reflection display section 9 and transmissiondisplay section 10 is 7.5 μm, and that the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17 isset in such a manner that reflection display section 9 can showsatisfactory reflection display by using the retardation suitable forthe transmission display.

[0301] To be more specific, in the present example, a liquid crystalcell for filling, including the liquid crystal layer having a thickness(d) of 7.5 μm in both the reflection display section 9 and transmissiondisplay section 10, is produced in the same manner as Example 1 exceptthat the insulation film 11 made of the insulation photosensitive resinis not formed on the substrate 5, and that, as shown in FIG. 4, theelectrode pattern is formed in such a manner that the electrode 7 of thereflection display section 9 and the electrode 7 of the transmissiondisplay section 10 are electrically isolated, so that a voltage isapplied to each separately from outside the liquid crystal cell.

[0302] Then, the liquid crystal layer 1 is produced by filling theliquid crystal composition having a difference of refractive index (Δn)of 0.065 and the positive dielectric constant anisotropy but the chiraldopant into the above liquid crystal cell for filling by means of vacuuminjection.

[0303] Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates. The lamination orientationof the phase difference compensation plates 16 and 17 and polarizationplates 14 and 15 is determined correspondingly to the alignmentdirection (alignment orientation) of the liquid crystal.

[0304] In the present example, the liquid crystal in the liquid crystallayer 1 is aligned in parallel with the substrates 4 and 5 (parallel tothe display surface) with no twist, and the birefringence mode using theretardation of the liquid crystal layer 1 for the display is adopted asthe liquid crystal display method.

[0305] Also, in the present example, the retardation suitable for thetransmission display is used for the reflection display section 9. Here,the transmission display section 10 is arranged in the same manner asits counterpart of Example 2 in Embodiment 2, while the reflectiondisplay section 9 is arranged differently from its counterpart ofExample 2 in that it has the liquid crystal layer as thick as the one inthe transmission display section 10. Thus, to assemble the liquidcrystal display of the present example, the liquid crystal display ofExample 2 is re-designed optically to determine the optical of thepolarization plates 14 and 15 and phase difference compensation plates16 and 17. In the present example, the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17 isdetermined in such a manner that satisfactory reflection display can beshown.

[0306] In the present example, like in Example 2, parallel aligningalignment films are used as the alignment films 2 and 3 to align theliquid crystal in parallel with the display surface when no voltage isapplied to the liquid crystal layer 1, and the alignment treatment isapplied to these alignment films 2 and 3 in such a manner as to form thecrossed rubbing angle of 180°.

[0307] In the above alignment treatment, the angle of twist of thedirector configuration of the liquid crystal (twist angle) is 0°, andthe alignment starts to change upon the voltage application from thecentral portion of the liquid crystal in the layer thickness directionof the liquid crystal layer 1.

[0308] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the liquid crystaldisplay of the present example is set forth in Table 3 below for readycomparison with reference to a common orientation.

[0309] The optical shown in Table 3 below is the position of eachoptical element on the display surface when the viewer observes thedisplay surface, and when the phase difference compensation plate 16 or17 is composed of more than one phase difference compensation plate,each phase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side.

[0310] Since the liquid crystal layer 1 is aligned without any twist,the alignment orientation set forth in Table 3 below is the alignmentorientation (alignment orientation of the major axis of the liquidcrystal molecules) in the entire liquid crystal layer 1 when no voltageis applied, and it is identical with the orientation of the rubbingtreatment applied to the alignment film 2 on the substrate 4 side.

[0311] Each orientation is expressed in degrees from the referencedirection set arbitrarily on the display surface, and the retardation ofeach phase difference compensation plate is expressed in nm with respectto a beam of monochrome light having the wavelength of 550 nm. TABLE 3EXAMPLE 7 3* 8 PLATE 14 TRANSMISSION AXIS 0 0 0 ORIENTATION (°) PLATEPLATE SLOW AXIS 15 15 15 16 ORIENTATION (°) RETARDATION (nm) 270 270 270PLATE SLOW AXIS 165 165 165 ORIENTATION (°) RETARDATION (nm) 135 135 135LC LAYER 1 ALIGNMENT ORIENTA- 75 75 75 TION (°) PLATE PLATE SLOW AXIS 75105 165 17 ORIENTATION (°) RETARDATION (nm) 135 270 70 PLATE SLOW AXIS135 — 135 ORIENTATION (°) RETARDATION (nm) 270 — 270 PLATE 15TRANSMISSION AXIS 60 0 60 ORIENTATION (°)

COMPARATIVE EXAMPLE 4

[0312] A comparative liquid crystal display of the present comparativeexample is assembled in the same manner as Example 7 except that theliquid crystal in the liquid crystal layer 1 is aligned in parallel withthe substrates 4 and 5 (parallel to the display surface) and twisted by70°, and that the polarization converting function of the liquid crystallayer 1 effected by the twisted director configuration of the liquidcrystal layer 1 is used for the display.

[0313] To be more specific, in the present comparative example, a liquidcrystal cell for filling, including the liquid crystal layer having athickness (d) of 4.5 μm in both the reflection display section 9 andtransmission display section 10, is produced in the same manner asExample 1 except that the insulation film 11 made of the insulationphotosensitive resin is not formed on the substrate 5, and that, asshown in FIG. 4, the electrode pattern is formed in such a manner thatthe electrode 7 of the reflection display section 9 and the electrode 7of the transmission display section 10 are electrically isolated, sothat a voltage is applied to each separately from outside the liquidcrystal cell.

[0314] Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,each of the phase difference compensation plates 16 and 17 is composedof two phase difference compensation plates. The lamination orientationof the phase difference compensation plates 16 and 17 and polarizationplates 14 and 15 is determined correspondingly to the alignmentdirection (alignment direction) of the liquid crystal.

[0315] Further, in the present comparative example, parallel aligningalignment films are used as the alignment films 2 and 3, so that thedirector configuration of the liquid crystal is parallel to the displaysurface when no voltage is applied, and the rubbing treatment is appliedthese alignment films 2 and 3 in such a manner as to form the crossedrubbing angle of 250°. The crossed rubbing angle is defined as above.Then, the liquid crystal layer 1 is produced by filling the liquidcrystal composition having a difference of refractive index (Δn) of0.065 and positive dielectric constant anisotropy into a space betweenthe electrode substrates of the liquid crystal cell for filling by meansof vacuum injection. The above alignment treatment and the function ofthe chiral dopant added to the liquid crystal composition impart theangle of twist (twist angle) of 70° to the director configuration of theliquid crystal. A concentration of the chiral dopant is adjusted toimpart the above specified twist angle. The liquid crystal layer 1aligned in this manner starts to change its alignment upon applicationof the voltage from the central portion thereof in its layer thicknessdirection.

[0316] Also, in the present comparative example, the product (Δn·d) of adifference of the refractive index (Δn) of the liquid crystalcomposition and a thickness (d) of the liquid crystal layer suitable forthe reflection display is used for the transmission display section 10.Here, the reflection display section 9 is arranged in the same manner asits counterpart of Example 5 in Embodiment 2, while the transmissiondisplay section 10 is arranged differently from its counterpart ofExample 5 in Embodiment 2 in that it has the same liquid crystal layerthickness as the one in the reflection display section 9. Thus, toassemble the comparative liquid crystal display of the presentcomparative example, the liquid crystal display of Example 5 isre-designed optically to determine the optical of the polarizationplates 14 and 15 and phase difference compensation plates 16 and 17. Inthe present comparative example, the optical of the polarization plates14 and 15 and phase difference compensation plates 16 and 17 isdetermined in such a manner that the transmission display section 10 canshow satisfactory dark display.

[0317] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the comparative liquidcrystal display of the present comparative example is set forth in Table4 below for ready comparison with a reference to a common orientation.

COMPARATIVE EXAMPLE 5

[0318] In the present comparative example, a comparative liquid crystaldisplay is assembled in the same manner as Comparative Example 4 exceptthat the polarization plates 14 and 15 and phase difference compensationplates 16 and 17 are optically positioned in such a manner that thetransmission display section 10 can show satisfactory light display. Tobe more specific, a comparative liquid crystal display is assembled inthe same manner as Example 7 except that: (1) the polarization plates 14and 15 and phase difference compensation plates 16 and 17 are opticallypositioned in such a manner that the transmission display section 10 canshow satisfactory light display, (2) the liquid crystal in the liquidcrystal layer 1 is aligned in parallel with the substrates 4 and 5(parallel to the display surface) and twisted by 70°, and (3) thepolarization converting function of the liquid crystal layer 1 effectedby the twisted alignment thereof is used for the display.

[0319] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the comparative liquidcrystal display of the present comparative example is set forth in Table4 below for ready comparison with reference to a common orientation.

EXAMPLE 9

[0320] In the present example, a liquid crystal display is assembled inthe same manner as Example 8 except that (1) the phase differencecompensation plate 16 is composed of two phase difference compensationplates while the phase difference compensation plate 17 is composed of asingle phase difference compensation plate, (2) the liquid crystal inthe liquid crystal layer 1 is aligned in parallel with the substrates 4and 5 (parallel to the display surface) and twisted by 70°, and (3) thepolarization converting function of the liquid crystal layer 1 effectedby the twisted alignment thereof is used for the display.

[0321] To be more specific, in the present example, a liquid crystalcell for filling, including the liquid crystal layer having a thickness(d) of 7.5 μm both in the reflection display section 9 and transmissiondisplay section 10, is produced in the same manner as Example 1 exceptthat the insulation film 11 made of the insulation photosensitive resinis not formed on the substrate 5, and that, as shown in FIG. 4, theelectrode pattern is formed in such a manner that the electrode 7 of thereflection display section 9 and the electrode 7 of the transmissiondisplay section 10 are electrically isolated, so that a voltage isapplied to each separately from outside the liquid crystal cell.

[0322] Further, the phase difference compensation plates 16 and 17 andpolarization plates 14 and 15 are laminated to the outside of therespective electrode substrates of the above liquid crystal cell. Here,the phase difference compensation plate 17 is composed of a single phasedifference compensation plate, while the phase difference compensationplate 16 is composed of two phase difference compensation plates. Thelamination orientation of the phase difference compensation plates 16and 17 and polarization plates 14 and 15 is determined correspondinglyto the alignment direction (alignment orientation) of the liquidcrystal.

[0323] In the present example, the liquid crystal display is assembledin such a manner that the twist director configuration of the liquidcrystal layer 1 (angle of twist of the director configuration of theliquid crystal (twist angle)) is 70°. More specifically, parallelaligning alignment films are used as the alignment films 2 and 3, sothat the director configuration of the liquid crystal is parallel to thedisplay surface when no voltage is applied, and the alignment treatmentis applied to these alignment films 2 and 3 by means of rubbing in sucha manner as to form the crossed rubbing angle of 250°. The crossedrubbing angle is defined as above. Then, the liquid crystal layer 1 isproduced by filling the liquid crystal composition having a differenceof refractive index (Δn) of 0.065 and positive dielectric constantanisotropy into a space between the electrode substrates of the liquidcrystal cell for filling by means of vacuum injection. The abovealignment treatment and the function of the chiral dopant added to theliquid crystal composition impart the angle of twist (twist angle) of70° to the director configuration of the liquid crystal. A concentrationof the chiral dopant is adjusted in such a manner as to impart the abovespecified twist angle to the director configuration of the liquidcrystal. The liquid crystal layer 1 aligned in this manner starts tochange its alignment upon the voltage application from the centralportion thereof in its layer thickness direction.

[0324] In the present example, the product (Δn·d) of a difference of therefractive index (Δn) of the liquid crystal composition and a thickness(d) of the liquid crystal layer suitable for the transmission display isused for the reflection display section 9. Here, the transmissiondisplay section 10 is arranged in the same manner as its counterpart ofExample 5 in Embodiment 2, while the reflection display section 9 isarranged differently from its counterpart of Example 5 in that it hasthe same liquid crystal layer thickness as the one in the transmissiondisplay section 10. Thus, to assemble the liquid crystal display of thepresent example, the liquid crystal display of Example 5 is re-designedoptically to determine the optical of the polarization plates 14 and 15and phase difference compensation plates 16 and 17. In the presentexample, the optical of the polarization plates 14 and 15 and phasedifference compensation plates 16 and 17 is determined in such a mannerthat satisfactory reflection display can be shown.

[0325] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the liquid crystaldisplay of the present example is set forth in Table 4 below for readycomparison with reference to a common orientation.

[0326] The optical shown in Table 4 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and when the phase difference compensation plate 16 or 17 iscomposed of more than one phase difference compensation plate, eachphase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side. Also, in Table 4, each orientation isexpressed in degrees from the reference orientation set arbitrarily onthe display surface, and the retardation of each phase differencecompensation plate is expressed in nm with respect to a beam ofmonochrome light having the wavelength of 550 nm. TABLE 4 EXAMPLE 4* 5*9 PLATE 14 TRANSMISSION AXIS 0 0 0 ORIENTATION (°) PLATE PLATE SLOW AXIS18 18 18 16 ORIENTATION (°) RETARDATION (nm) 270 270 127 PLATE SLOW AXIS126 126 126 ORIENTATION (°) RETARDATION (nm) 135 135 135 LC LAYER 1SUBSTRATE 4 ALIGNMENT 16 16 16 ORIENTATION (°) SUBSTRATE 5 ALIGNMENT 8686 86 ORIENTATION (°) PLATE PLATE SLOW AXIS 36 36 −4 17 ORIENTATION (°)RETARDATION (nm) 135 135 260 PLATE SLOW AXIS 96 108 — ORIENTATION (°)RETARDATION (nm) 270 270 — PLATE 15 TRANSMISSION AXIS 21 0 152ORIENTATION (°)

[0327] As has been explained, in the liquid crystal display of Example 7and the comparative liquid crystal displays of Comparative Examples 3through 5, a thickness (d) of the liquid crystal layer is set to 4.5 μm,so that satisfactory reflection display can be shown. Thus, in Example 7and Comparative Examples 3 through 5, the optical of the polarizationplate 14 and phase difference compensation plate 16, which areresponsible for the reflection display alone, is set to be suitable forthe reflection display. On the other hand, the thickness of the liquidcrystal layer of the transmission display section 10 is set differentlyfrom the one in its counterpart of each Example in Embodiment 2. Thus,in Example 7 and Comparative Examples 3 through 5, the optical of thephase difference compensation plate 17 and polarization plate 15 is setindividually in accordance with the optical characteristics of thetransmission display section 10. In other words, in Example 7 andComparative Example 4, the liquid crystal displays which can realize thesatisfactory dark display are assembled, and in Comparative Examples 3and 5, the liquid crystal displays which can realize satisfactory lightdisplay are assembled.

[0328] In contrast, in the liquid crystal displays of Examples 8 and 9,a thickness (d) of the liquid crystal layer is set to 7.5 μm, so thatsatisfactory transmission display can be shown. For this reason, inExamples 8 and 9, the optical of the polarization plate 14, phasedifference control plates 16 and 17, and polarization plate 15 is set tobe suitable for the transmission display. Thus, in Examples 8 and 9, thedisplay characteristics of the reflection display section 9 aredetermined by the optical of the polarization plate 14 and phasedifference compensation plate 16 whose optical is set for thetransmission display.

[0329] In addition, the display characteristics of the liquid crystaldisplays assembled in Example 7, Comparative Example 3, Example 8,Comparative Examples 4 and 5, and Example 9 are graphed in FIGS. 11through 15, respectively. These display characteristics were measuredthrough the microscope in the same manner as Example 1, and in eachdrawing, the horizontal axis represents a root mean square value of theapplied voltage, and the vertical axis represents the brightness(reflectance or transmittance). Here, the transmittance of thetransmitting display section 10 when the polarization plates 14 and 15are not provided is scaled as 100%, and the reflectance of thereflection display section 9 before the polarization plate 14 isprovided is scaled as 100%.

[0330] In FIG. 11, a curve 261 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 262 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 7.

[0331]FIG. 11 reveals that, in Example 7, while the applied voltage isin a range between 1V and 3V, the transmittance increases with anincreasing applied voltage. On the other hand, the reflectance increaseswith an increasing applied voltage while the applied voltage is in arange between 1V and 2V, and decreases with an increasing appliedvoltage after the applied voltage exceeds 2V. That is, when the appliedvoltage is 1V, the reflectance of the reflection display section 9 andthe transmittance of the transmission display section 10 are both 3%.When the applied voltage is increased to 2V, both increase to 40% and18%, respectively, and when the applied voltage is increased further to3V, the reflectance of the reflection display section 9 decreases to28%, while the transmittance of the transmission display sectionincreases further to 33%.

[0332] In FIG. 12, a curve 271 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 272 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Comparative Example 3.

[0333]FIG. 12 reveals that, in Comparative Example 3, while the appliedvoltage is in a range between 1V and 2V, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 18%, respectively, and when the applied voltage is increasedto 2V, both increase to 40%.

[0334] In FIG. 13, a curve 281 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 282 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 8.

[0335]FIG. 13 reveals that, in Example 8, while the applied voltage isin a range between 1V and 2V, the transmittance increases with anincreasing applied voltage. On the other hand, the reflectance increaseswith an increasing applied voltage when the applied voltage is in arange between 0.7V and 1.2V, decreases with an increasing appliedvoltage when the applied voltage is in a range between 1.2V and 1.7V,and increases again with an increasing applied voltage when the appliedvoltage is in a range between 1.7V and 2.3V. That is, when the appliedvoltage is 1V, the reflectance of the reflection display section 9 andthe transmittance of the transmission display section 10 are 24% and 3%,respectively. When the applied voltage is increased to 1.2V, thereflectance of the reflection display section 9 increases to 40%. Whenthe applied voltage is further increased to 1.7V, the reflectance of thereflection display section 9 decreases to 3%. When the applied voltageis further increased to 2V, both the reflectance of the reflectiondisplay section 9 and the transmittance of the transmission displaysection 10 increase to 27% and 39%, respectively.

[0336] In FIG. 14, a curve 291 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 292 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Comparative Example 4.

[0337]FIG. 14 reveals that, in Comparative Example 4, while the appliedvoltage is in a range between 1.2V and 3V, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1.2V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 1%, respectively, and when the applied voltage is increasedto 3V, both increase to 36% and 16%, respectively.

[0338] In FIG. 15, a curve 311 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 312 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Comparative Example 5.

[0339]FIG. 15 reveals that, in Comparative Example 5, while the appliedvoltage is in a range between 1.2V and 3V, both the reflectance andtransmittance increase with an increasing applied voltage. That is, whenthe applied voltage is 1.2V, the reflectance of the reflection displaysection 9 and the transmittance of the transmission display section 10are 3% and 21%, respectively, and when the applied voltage is increasedto 3V, both increase to 39% and 35%, respectively.

[0340] In FIG. 16, a curve 321 represents the voltage dependence of thereflectance of the reflection display section 9 versus a voltage acrossthe electrodes 6 and 7, and a curve 322 represents the voltagedependence of the transmittance of the transmission display section 10versus a voltage across the electrodes 6 and 7 in the liquid crystaldisplay assembled in Example 9.

[0341]FIG. 16 reveals that, in Example 9, while the applied voltage isin a range between 1.2V and 3V, the transmittance increases with anincreasing applied voltage. On the other hand, when the applied voltageis in a range between 0.9 and 1.7V, the reflectance decreases with anincreasing applied voltage, and then increases with an increasingapplied voltage. That is, when the applied voltage is 1.2V, thereflectance of the reflection display section 9 and the transmittance ofthe transmission display section 10 are 7 and 32%, respectively, andwhen the applied voltage is increased to 1.7V, the reflectance of thereflection display section 9 decreases to 3%, and when the appliedvoltage is further increased to 3V, both the reflectance of thereflection display section 9 and the transmittance of the transmissiondisplay section 10 increase to 37% and 36%, respectively.

[0342] The above Examples and Comparative Examples discussed a liquidcrystal display exploiting the change in the polarization state causedby the polarization converting function of the liquid crystal layer 1,such as retardation and optical rotatory polarization, provided with thepolarization plates 14 and 15, and having equal thicknesses of theliquid crystal layer 1 in the reflection display section 9 andtransmission display section 10. In this case, when the same voltage isapplied to the respective electrodes 7 of the reflection display section9 and transmission display 10 (when the reflection display section 9 andtransmission display section 10 are driven by the same voltage), if, asin Example 7 and Comparative Examples 3 through 5, a voltage which canattain satisfactory brightness and contrast ratio for the light displayin the reflection display section 9 is applied, the brightness andcontrast ratio for the light display in the transmission display section10 are not satisfactory, and if, as in Example 7 and ComparativeExamples 3 through 5, a voltage which can attain satisfactory brightnessand contrast ratio for the light display in the transmission displaysection 10 is applied, the brightness in the reflection display section9 and the brightness in the transmission display section 10 do notchange in the same manner, thereby making satisfactory displayimpossible.

[0343] However, the liquid crystal displays of Examples 7 through 9 cansolve the above problem and show satisfactory display by applyingdifferent voltages to the respective electrodes 7 in the reflectiondisplay section 9 and transmission display section 10 (by driving thereflection display section 9 and transmission display section 10 usingdifferent respective voltages).

[0344] In other words, any of the liquid crystal displays of Examples 7through 9 can attain satisfactory brightness and contrast ratio for thelight display both in the reflection display section 9 and transmissiondisplay section 10 by applying different respective voltages to theelectrode 7 of the transmission display section 10 and the electrode 7of the reflection display section 9. At the same time, the reflectiondisplay section 9 and transmission display section 10 can show the samedisplay state, that is, either the light or dark display, therebyrealizing the display with excellent visibility.

[0345] It is understood from the comparison of the present embodimentand Embodiment 2 that it is effective to make the liquid crystal layer 1thicker in the transmission display section 10 than in the reflectiondisplay section 9 to attain the satisfactory brightness and contrastratio for the light display both in the reflection display section 9 andtransmission display section 10 of the liquid crystal display using thepolarization converting function, such as the retardation and opticalrotatory polarization of the liquid crystal layer 1, with the use of thepolarization plates 14 and 15.

[0346] In the liquid crystal display mode adopted in each example of thepresent embodiment and Embodiment 2, the director configuration of theliquid crystal when no voltage is applied is parallel to the planesurface direction of the display surface. It should be appreciated that,however, other modes, such as vertical alignment mode and hybridalignment mode, are also applicable by using the liquid crystalmaterials of different kinds from those disclosed in the above examplesor using the alignment film having different properties from those ofthe alignment film disclosed above.

[0347] Further, it should be appreciated that satisfactory opticalcharacteristics can be attained by the present invention using anyliquid crystal display mode which exploits the retardation or opticalrotatory polarization of the liquid crystal layer 1, provided that, inthe display mode used, the thickness of the liquid crystal layer affectsthe optical characteristics, and that a liquid crystal layer thicknesswhich is thinner in the reflection display section 9 than in thetransmission display section 10 is suitable for the display mode used.

[0348] Furthermore, it is understood that the liquid crystal displays ofExamples 4 and 7 through 9 can show the satisfactory display whensupplied with different voltages to the reflection display section 9 andtransmission display section 10 by means of the electrodes 6 and 7(alignment mechanism). In this case, the liquid crystal displays ofExamples 4 and 7 can show satisfactory display when a sufficiently highvoltage is applied to the transmission display section 10. Also, theliquid crystal displays of Examples 8 and 9 can show satisfactorydisplay by adjusting the voltage at the reflection display section 9.Thus, according to the present embodiment and Embodiment 2, satisfactorydisplay can be shown by producing the liquid crystal cell beforehand insuch a manner that different voltages can be applied to the reflectiondisplay section 9 and transmission display section 10, besides bychanging the thickness of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10.

Embodiment 4

[0349] Explained in the present embodiment is a liquid crystal displaywhich can realize satisfactory reflection display and transmissiondisplay by providing different director configurations of the liquidcrystal in the reflection display section and transmission displaysection by changing the alignment treatment orientation (rubbingorientation) on the substrate, which is a factor that determines thedirector configuration of the liquid crystal, that is, the alignmenttreatment orientation of the alignment film provided to each electrodesubstrate in the reflection display section and transmission displaysection.

[0350] In the present embodiment, a so-called rubbing method is adoptedto align the liquid crystal layer uniformly. In the present embodiment,at least two different director configurations of the liquid crystal canbe realized by covering the surface of the alignment film with thephotoresist or the like before subjecting the alignment film to therubbing treatment, so that the alignment film provided to each electrodesubstrate can be given different respective alignment treatmentorientations in the reflection display section and transmission displaysection. According to the above method, the director configuration ofthe liquid crystal suitable for the reflection display and the directorconfiguration of the liquid crystal suitable for the transmissiondisplay can be realized at the same time, thereby realizing satisfactoryreflection display and transmission display.

[0351] In the following, the liquid crystal display of the presentembodiment will be explained in detail, and hereinafter, like componentsare labeled with like reference numerals with respect to Embodiments 1through 3, and, for ease of explanation, the description of thesecomponents is not repeated here.

[0352] In the first place, the process of alignment treatment of thesubstrate (electrode substrate 40) used in the liquid crystal display ofthe present embodiment will be explained with reference to FIGS. 17 and18(a) through 18(e).

[0353] As shown in FIG. 18(a), an alignment film material is appliedover a substrate 41 (equivalent to the substrate 4 on which is formedthe electrode 6 or the substrate 5 on which are formed the electrodes 7)of the liquid crystal cell on the surface thereof touching the liquidcrystal layer 1 (S1). Then, the alignment film material is pre-baked(S2) and cured (S3), whereby an alignment film 42 (equivalent to thealignment film 2 or 3) is formed over the substrate 41 on the surfacethereof touching the liquid crystal layer 1.

[0354] Then, the alignment film 42 is subjected to the rubbingtreatment, and as a consequence, the alignment treatment is applied tothe electrode substrate 40 which includes the alignment film 42 at theinterface with the liquid crystal layer 1 of the substrate 41. Here, inthe present embodiment, as shown in FIG. 18(b), screening is carried outby a screen resist 43 for the rubbing treatment, so that the rubbingtreatment is applied partially. In this case, a resist material for thescreen for the rubbing treatment is applied over the alignment film 42(S4). Then, the resist material is pre-baked (S5), exposed to UV rayswith masking to expose portions (first alignment treatment regions 42 a)of the alignment film 42 (S6), developed (S7), and cured (S8), afterwhich the rubbing treatment is applied to the first alignment treatmentregions 42 a (S9). Then, after the rubbing treated electrode substrate40 is cleaned (S10), the resist 43 is removed as shown in FIG. 18(c)(S11).

[0355] Subsequently, to realize an director configuration of the liquidcrystal different from the director configuration of the liquid crystalon the first alignment treatment regions 42 a, as shown in FIG. 18(d),rubbed portions (first alignment treatment regions 42 a) are protectedby a screen resist 44 for the rubbing treatment, and the rubbingtreatment is applied to portions which have not been rubbed. To be morespecific, a resist material of the screen for the rubbing treatment isapplied over the alignment film 42 from which the resist 43 was removed(S12). Then, the resist material is pre-baked (S13), exposed to UV rayswith masking in such a manner that portions (second alignment treatmentregions 42 b) other than the first alignment treatment regions 42 a onthe alignment film 42 are exposed (S14), developed (S15), and cured(S16). Subsequently, the second alignment treatment regions 42 b aresubjected to the rubbing treatment in such a manner that the treatmentorientations are different in the first and second alignment treatmentregions 42 a and 42 b (S17). Then, after the rubbing treated electrodesubstrate 40 is cleaned (S18), the resist 44 is removed as shown in FIG.18(e) (S19). Consequently, the alignment film 42 (alignment mechanism),to which the alignment treatment has been applied twice in differentorientations, is obtained.

[0356] As has been explained, in the present embodiment, the alignmenttreatment is applied at least twice with the patterning by means of theresist. Here, at least two different director configurations of theliquid crystal (for example, various kinds of planer alignments havingtheir respective aligning directions) can be obtained by changing thetreatment orientation for each alignment treatment (in the aboveexplanation, the alignment treatment is effected in two differentorientations by applying the alignment treatment twice). If thealignment treatment orientation is changed on at least one of thesubstrates (electrode substrates) in the above manner, the alignmentsare provided to the reflection display section 9 and transmissiondisplay section 10 independently, thereby making it possible to realizesatisfactory display.

[0357] Next, a liquid crystal display having different directorconfigurations of the liquid crystal in the reflection display section 9and transmission display section 10 and using the polarization plates 14and 15 will be explained by way of examples for purposes of explanationonly, without any intention as a definition of the limits of theinvention.

EXAMPLE 10

[0358] In the present example, a liquid crystal display is assembled inthe same manner as Comparative Example 5. To be more specific, a liquidcrystal cell for filling, including the liquid crystal layer having athickness (d) (cell gap) of 4.5 μm both in the reflection displaysection 9 and transmission display section 10, is produced in the samemanner as Example 1 except that the insulation film 11 made of theinsulation photosensitive resin is not formed on the substrate 5, andthat, as shown in FIG. 4, the electrode pattern is formed in such amanner that the electrode 7 of the reflection display section 9 and theelectrode 7 of the transmission display section 10 are electricallyisolated, so that a voltage is applied to each separately from outsidethe liquid crystal cell. Then, the phase difference compensation plates16 and 17 and polarization plates 14 and 15 are laminated to the outsideof the respective electrode substrates of the above liquid crystal cell.Here, each of the phase difference compensation plates 16 and 17 iscomposed of two phase difference compensation plates.

[0359] In the present example, the alignment film 3 is subjected to therubbing treatment in different orientations in the same manner as shownin FIGS. 17 and 18(a) through 18(e). To be more specific, in the presentexample, the alignment film 2 on the substrate 4 side is rubbed in thesame orientation both in the reflection display section 9 andtransmission display section 10, whereas the alignment film 3 (alignmentmechanism) on the substrate 5 side is rubbed in such a manner thealignment orientations of the liquid crystal are different in thereflection display section 9 and transmission display section 10.

[0360] In the present example, the reflection display section 9 adopts aliquid crystal display mode, in which the liquid crystal is aligned inparallel with the display surface (parallel to the substrates 4 and 5)with a twist, and the transmission display section 10 adopts a liquidcrystal display mode, in which the liquid crystal is aligned in parallelwith the display surface (parallel to the substrates 4 and 5) withouttwist.

[0361] Also, in the present example, the liquid crystal display isassembled in such a manner that, in the reflection display section 9,Δn·d of the liquid crystal layer 1 is approximately 270 nm and the angleof twist of the director configuration of the liquid crystal (twistangle) is 70°, and in the transmission display section 10, Δn·d of theliquid crystal layer 1 is approximately 270 nm and the angle of twist ofthe liquid crystal (twist angle) is 0°. Thus, the liquid crystal displayassembled in the above manner can show satisfactory display both in thereflection display section 9 and transmission display section 10 whilehaving the liquid crystal layer 1 provided continuously across thereflection display section 9 and transmission display section 10 withoutchanging the cell gap.

[0362] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the reflection displaysection 9 and transmission display section 10 in the liquid crystaldisplay of the present example is set forth in Table 5 below for readycomparison with reference to a common orientation.

[0363] The optical shown in Table 5 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and when the phase difference compensation plate 16 or 17 iscomposed of more than one phase difference compensation plate, eachphase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side. Also, in Table 5, each orientation isexpressed in degrees from the reference orientation set arbitrarily onthe display surface, and the retardation of each phase differencecompensation plate is expressed in nm with respect to a beam ofmonochrome light having the wavelength of 550 nm. TABLE 5 EXAMPLE 10SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0 ORIENTATION (°) PLATE PLATESLOW AXIS ORIENTATION (°) 15 16 RETARDATION (nm) 270 PLATE SLOW AXISORIENTATION (°) 75 RETARDATION (nm) 135 LC LAYER 1 SUBSTRATE 4 −15 −15ALIGNMENT ORIENTATION (°) SUBSTRATE 5 55 −15 ALIGNMENT ORIENTATION (°)PLATE PLATE SLOW AXIS ORIENTATION (°) −15 17 RETARDATION (nm) 115 PLATESLOW AXIS ORIENTATION (°) −75 RETARDATION (nm) 270 PLATE 15 TRANSMISSIONAXIS 90 ORIENTATION (°)

[0364] Next, the operation of each optical element in the presentembodiment will be explained in the following.

[0365] First, a case where no voltage is applied to the liquid crystallayer 1 will be explained. In this case, the liquid crystal in theliquid crystal layer 1 is aligned along the alignment of the interfaceof the substrate touching the liquid crystal layer 1, that is, thealignment treatment orientation of the alignment films 2 and 3 providedon their respective electrode substrates. For example, when the chiraldopant is not added to the liquid crystal composition in the liquidcrystal display of Example 10, the liquid crystal is twisted 70° to theleft in the reflection display section 9, and 0°, that is, not twisted,in the transmission display section 10.

[0366] For this reason, if no voltage is applied to the liquid crystallayer 1, given 270 nm as Δn·d of the liquid crystal layer 1, circularlypolarized light entering the liquid crystal layer 1 is converted tolinearly polarized light before it exits from the reflection displaysection 9. Thus, light entering the liquid crystal layer 1 from thepolarization plate 14 side is converted to circularly polarized light bythe phase different compensation plate 16, then converted to linearlypolarized light by the liquid crystal layer 1, which exits from theliquid crystal layer 1 and reaches the reflection film 8. If thelinearly polarized light is reflected by the reflection film 8, thereflected light is converted again into the transmission components ofthe polarization plate 14. Consequently, in the above liquid crystaldisplay, the reflection display section 9 shows light display when novoltage is applied to the liquid crystal layer 1.

[0367] On the other hand, if no voltage is applied to the liquid layer1, given 250 nm-270 nm as Δn·d of the liquid crystal layer 1, the liquidcrystal layer 1 functions as the ½ wavelength plate in the transmissiondisplay section 10. To be more specific, circularly polarized lightentering the liquid crystal layer 1 is converted to another circularlypolarized light that is orthogonal to the incident circularly polarizedlight at right angles. For example, if the incident circularly polarizedlight is right, then it is converted to left circularly polarized light,and if the incident circularly polarized is left, then it is convertedto right circularly polarized light. In the transmission display section10, the incident light passes through the polarization plate 15, andenters the liquid crystal layer 1 after it is converted to circularlypolarized light by the phase difference compensation plate 17. InExample 10, substantially left circularly polarized light enters theliquid crystal layer 1 from the phase difference compensation plate 17,and is converted to right circularly polarized light. Here, rightcircularly polarized light is converted to linearly polarized lightalong the transmission axis direction of the polarization plate 14 bythe phase difference compensation plate 16, while left circularlypolarized light is converted to linearly polarized light along theabsorption axis direction of the polarization plate 14. Thus, thetransmission display section 10 of the above liquid crystal displayshows light display when no voltage is applied to the liquid crystallayer 1.

[0368] Next, a case where a voltage is applied to the liquid crystallayer 1 will be explained. While a voltage is applied to the liquidcrystal layer 1, the liquid crystal in the liquid crystal layer 1 isaligned perpendicular to the substrates 4 and 5 in response to theapplied voltage in both the reflection display section 9 andtransmission display section 10, whereby the above polarizationconverting function becomes less effective. In other words, the incidentcircularly polarized light from the phase difference compensation plates16 and 17 passes through the liquid crystal layer 1 directly.Consequently, both the reflection display section 9 and transmissiondisplay section 10 show the dark display.

[0369] In Example 10, the phase difference compensation plate 17 iscomposed of a phase difference compensation plate having the retardationof 115 nm. It is preferable that the phase difference compensation plate17 has the retardation of about 135 nm to realize satisfactorycircularly polarized light by the phase difference compensation plate 17alone. However, the retardation of the liquid crystal layer 1 in thetransmission display section 10 is not lost completely at a practicalvoltage level, and in consideration of this fact, the retardation of thephase difference compensation plate 17 is set in such a manner as toobtain satisfactory contrast.

[0370] The phase difference compensation plate 16 is furnished with afunction of converting light entering the liquid crystal layer 1 in thereflection display section 9 into circularly polarized light with awavelength in a broad range. In the above liquid crystal display, theliquid crystal layer 1 in the reflection display section 9 is twisted70°, and Δn·d thereof is set to 270 nm. Thus, circularly polarized lightenters the liquid crystal layer 1 in the reflection display section 9,and is converted to linearly polarized light by the liquid crystal layer1 while it passes through the same and reaches the reflection film 8.Then, the linearly polarized light having reached the reflection film 8is reflected on the mirror surface thereof, and passes through eachoptical element in the reversed order. Consequently, the reflected lightis converted to linearly polarized light having an oscillating electricfield along the transmission axis orientation of the polarization plate14. Hence, the reflection display section 9 shows the light display.

[0371] Here, the liquid crystal composition used herein is blended withthe chiral dopant for imparting a natural twist to the left to thedirector configuration of the liquid crystal. The chiral dopant changesthe natural helical pitch of the liquid crystal composition depending onits concentration in the liquid crystal composition. Thus, by exploitingthe fact that the lowest voltage at which the director configuration ofthe liquid crystal starts to change varies with the helical pitch, thevoltage dependencies of the brightness in the reflection display section9 and transmission display section 10 can be matched if the helicalpitch is adjusted adequately.

[0372] The display characteristics of the liquid crystal display ofExample 10 assembled in the above manner are graphed in FIG. 19. Thedisplay characteristics of FIG. 19 were measured in the same manner asExample 1, and in the drawing, the horizontal axis represents a rootmean square value of the applied voltage and the vertical axisrepresents the brightness (reflectance or transmittance).

[0373] In FIG. 19, a curve 331 indicates the voltage dependence of thereflectance of the reflection display section 9, and a curve 332indicates the voltage dependence of the transmittance of thetransmission display section 10 in the liquid crystal display of Example10.

[0374] As can be understood from FIG. 19, the liquid crystal display ofExample 10 shows the light display when no voltage is applied, and itcan realize the display in the so-called normally white (NW) mode, inwhich both the reflectance and transmittance decrease with an increasingapplied voltage. In the present liquid crystal display, not only can thecontrast ratio be set to substantially the same value in the reflectiondisplay section 9 and transmission display section 10, but also thereflection display section 9 and transmission display section 10 canshow either the dark or light display simultaneously, thereby realizingthe display with excellent visibility.

[0375] As has been explained, setting different twist angles of theliquid crystal layer 1 in the reflection display section 9 andtransmission display section 10 as the means for changing the directorconfiguration of the liquid crystal in the reflection display section 9and transmission display section 10 is effective to realize satisfactorydisplay both in the reflection display section 9 and transmissiondisplay section 10.

[0376] In Example 10, to change the twist angle of the liquid crystallayer 1 in the reflecting display section 9 and transmission displaysection 10, the rubbing treatment is applied in different orientationsin the reflecting display section 9 and transmission display section 10,so that the director configuration of the liquid crystal layer 1 istwisted in the reflection display section 9 but not in the transmissiondisplay section 10. However, means for changing the twist angle of theliquid crystal layer 1 in the reflection display section 9 andtransmission display section 10 is not especially limited.

[0377] For example, besides the above combination, the followingcombinations are applicable: (1) the director configuration of theliquid crystal layer 1 is twisted in both the reflecting display section9 and transmission display section 10, but the twist angles or theorientations of the twist are different; (2) the director configurationof the liquid crystal layer 1 is twisted in the transmission displaysection 10 but not in the reflection display section 9; (3) the tilts(so-called pre-tilts) of the liquid crystal with respect to thesubstrates 4 and 5 are different in the reflection display section 9 andtransmission display section 10; (4) the change of the directorconfiguration of the liquid crystal at the substrate interface iscombined with other means of the present invention; (5) different cellgaps are provided to the reflection display section 9 and transmissiondisplay section 10; and (6) different electric fields are generated inthe reflection display section 9 and transmission display section 10.

Embodiment 5

[0378] In each example of Embodiments 2 through 4, the arrangement forrealizing satisfactory reflection display and transmission display onthe liquid crystal display using the liquid crystal aligned in parallelwith the substrates was explained. In the present embodiment, a liquidcrystal display whose alignment orientation of the liquid crystal isperpendicular to the substrates, like the one in Example 1 of Embodiment1, will be explained. Note that, however, the dichroic dye is notblended in the liquid crystal layer, and the liquid crystal display isdesigned in such a manner as to show the display using the polarizationplate while exploiting the birefringence or optical rotatorypolarization (polarization converting function) of the liquid crystal.Hereinafter, like components are labeled with like reference numeralswith respect to Embodiments 1 through 4, and, for ease of explanation,the description of these components is not repeated here.

[0379] In the liquid crystal display of the present embodiment, liquidcrystal having negative dielectric constant anisotropy is used in theliquid crystal layer 1. Also, vertical aligning alignment films are usedfor the alignment films 2 and 3 for sandwiching the liquid crystal layer1. In this case, the liquid crystal molecules are aligned substantiallyperpendicular to the substrates 4 and 5 (display surface) when novoltage is applied to the liquid crystal layer 1, and start to tilt fromthe normal direction of the substrates 4 and 5 upon application of thevoltage, thereby effecting the polarization converting function to thelight passing through the liquid crystal layer 1 in the normal directionthereof.

[0380] The difference between the liquid crystal display of the presentembodiment and the counterpart using the alignment films 2 and 3 thatalign the liquid crystal in parallel with the substrates is that, in theliquid crystal display of the present embodiment, the liquid crystal isaligned in the normal direction of the substrates 4 and 5, up to andincluding a layer at the interface between the liquid crystal layer 1and electrode substrate, even without applying a voltage. To exploitthese characteristics effectively, the NB (Normally Black) mode, inwhich the black display is shown when no voltage is applied, is used forthe liquid crystal display of the present embodiment. To be morespecific, the display is shown in the reflection display section 9 byallowing circularly polarized light to go into the liquid crystal layer1. In the transmission display section 10, circularly polarized light isalso allowed to go into the liquid crystal layer 1. Circularly polarizedlight is also used in the transmission display section 10 because thephase difference compensation plate 16 (which is also used in reflectiondisplay) affects the polarization of the light exiting the liquidcrystal layer 1, and in consideration of the fact that, in order to useelectrically connected electrodes to drive the liquid crystal layer 1 inboth the reflection display section 9 and transmission display section10, and in order to realize dark display in both sectionssimultaneously, the liquid crystal layer 1 is aligned perpendicular tothe substrates 4 and 5 in the transmission display section as well.Thus, with a combination of the polarization plates 14 and 15 and phasedifference compensation plates 16 and 17, of all the phase differencecompensation plates forming the phase difference compensation plate 17,the retardation of the one closest to the liquid crystal layer 1 is setto 135 nm. Consequently, the liquid crystal display of the presentembodiment can realize satisfactory NB display.

[0381] Next, the setting of the liquid crystal layer 1 so as to realizesatisfactory light display in the above combination of the polarizationplates 14 and 15 and the phase difference compensation plates 16 and 17will be explained.

[0382] As has been described above, in the present embodiment, thedirector configuration of the liquid crystal layer 1 starts to tilt fromthe normal direction of the substrates 4 and 5 upon voltage application.While the voltage is fully applied to the liquid crystal layer 1, it ispreferable that the liquid crystal layer 1 functions to convert thecircularly polarized light to the linearly polarized light in thereflection display section 9, and to convert the circularly polarizedlight to another circularly polarized light rotating in the reversedirection in the transmission display section 10. When the liquidcrystal layer 1 effects the above converting function, satisfactorylight display can be realized.

[0383] To allow the liquid crystal layer 1 to effect the aboveconverting function, for example, it is preferable that the alignmenttreatment is applied to the alignment films 2 and 3 in such a manner notto twist the liquid crystal, and that no chiral dopant is added to theliquid crystal composition. To be more specific, it is preferable that,when λ means the wavelength of incident light, retardation of the liquidcrystal layer varies by λ/4 in the reflection display section 9 and byλ/2 in the transmission display section 10 upon voltage application.

[0384] In case that the thicknesses of the liquid crystal layer 1 aredifferent in the refection display section 9 and transmission displaysection 10, the liquid crystal layer 1 can be readily set in theabove-described manner to effect the above converting function.

[0385] In the following, the liquid crystal display of the presentembodiment will be explained by way of examples for purposes ofexplanation only, without any intention as a definition of the limits ofthe invention.

EXAMPLE 11

[0386] In the present example, a liquid crystal cell for filling havingdifferent thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 is produced in thesame manner as Example 1. Here, vertical aligning alignment films whichalign the liquid crystal perpendicular to the substrates 4 and 5 areused as the alignment films 2 and 3. The alignment treatment is appliedto the alignment films 2 and 3 by means of rubbing, so that the liquidcrystal is aligned slightly tilted with respect to the normalorientation (perpendicular direction) of the substrates 4 and 5.

[0387] Note that, however, the thicknesses (d) of the liquid crystallayer are set to 3 μm and 6 μm in the reflection display section 9 andtransmission display section 10, respectively, and the liquid crystallayer 1 is made from a liquid crystal material, that is, liquid crystalhaving a difference of refractive index (Δn) of 0.06 and negativedielectric constant anisotropy. Then, the liquid crystal display isassembled by laminating the phase difference compensation plates 16 and17 and the polarization plates 14 and 15 to the outside of therespective electrode substrates of the above liquid crystal cell.Herein, each of the phase difference compensation plates 16 and 17 iscomposed of two phase difference compensation plates.

[0388] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the reflection displaysection 9 and transmission display section 10 in the liquid crystaldisplay of the present example is set forth in Table 6 below for readycomparison with reference to a common orientation.

[0389] The optical shown in Table 6 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and when the phase difference compensation plate 16 or 17 iscomposed of more than one phase difference compensation plate, eachphase difference compensation plate forming the phase differencecompensation plate 16 or 17 is set forth in accordance with the actualposition from the viewer's side. Also, in Table 6, each direction isexpressed in degrees from the reference direction set arbitrarily on thedisplay surface, and the retardation of each phase differencecompensation plate is expressed in nm with respect to a beam ofmonochrome light having the wavelength of 550 nm. TABLE 6 EXAMPLE 11SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0 ORIENTATION (°) PLATE PLATESLOW AXIS ORIENTATION (°) 15 16 RETARDATION (nm) 270 PLATE SLOW AXISORIENTATION (°) 75 RETARDATION (nm) 135 LC LAYER 1 SUBSTRATE 4 −15 −15ALIGNMENT ORIENTATION (°) SUBSTRATE 5 −15 −15 ALIGNMENT ORIENTATION (°)PLATE PLATE SLOW AXIS ORIENTATION (°) −15 17 RETARDATION (nm) 135 PLATESLOW AXIS ORIENTATION (°) −75 RETARDATION (nm) 270 PLATE 15 TRANSMISSIONAXIS 90 ORIENTATION (°)

[0390] The display characteristics of the liquid crystal display ofExample 11 assembled in the above manner are graphed in FIG. 20. Thedisplay characteristics of FIG. 20 were measured in the same manner asExample 1, and in the drawing, the horizontal axis represents a rootmean square value of the applied voltage and the vertical axisrepresents the brightness (reflectance or transmittance).

[0391] In FIG. 20, a curve 341 indicates the voltage dependence of thereflectance of the reflection display section 9, and a curve 342indicates the voltage dependence of the transmittance of thetransmission display section 10 in the liquid crystal display of Example11.

[0392] As can be understood from FIG. 20, the liquid crystal display ofExample 11 shows the dark display when no voltage is applied, and it canrealize the display in the so-called normally black (NB) mode, in whichthe reflectance and transmittance increase with an increasing appliedvoltage. In the present liquid crystal display, not only can thecontrast ratio be set to substantially the same value in the reflectiondisplay section 9 and transmission display section 10, but also thereflection display section 9 and transmission display section 10 showeither the dark or light display simultaneously, thereby realizing thedisplay with excellent visibility.

[0393] As has been explained, according to the present embodiment, it isconfirmed that a liquid crystal display of the transflective type canshow satisfactory display both in the reflection display section 9 andtransmission display section 10, if alignment means (vertical aligningalignment film) that aligns the liquid crystal perpendicular to thesubstrate surface touching the liquid crystal (liquid crystal layer 1)is provided to at least one of the reflection display section 9 andtransmission display section 10 in the liquid crystal display of thepresent invention, in which different director configurations of theliquid crystal are realized in the reflection display section 9 andtransmission display section 10 simultaneously.

Embodiment 6

[0394] Explained in the present embodiment is a liquid crystal displaywhich shows the display by changing the alignment orientation of theliquid crystal in response to a varying voltage while keeping thedirector configuration of the liquid crystal in parallel with thedisplay surface (substrate) in at least one of the reflecting displaysection 9 and transmission display section 10. In other words, in theliquid crystal display of the present embodiment, the liquid crystalmolecules start to rotate in parallel with the display surface(substrate) upon voltage application in at least one of the reflectiondisplay section and transmission display section.

[0395] In the following, the liquid crystal display of the presentembodiment will be explained by way of examples for purposes ofexplanation only, without any intention as a definition of the limits ofthe invention. Hereinafter, like components are labeled with likereference numerals with respect to Embodiments 1 through 5, and, forease of explanation, the description of these components is not repeatedhere.

EXAMPLE 12

[0396] Explained in the present example with reference to FIGS. 21(a)and 21(b) is a liquid crystal display furnished with an opticalswitching function, in which the liquid crystal molecules are rotated inparallel with the substrate by means of a transverse electric field (inthe in-plane direction with respect to the substrate), by adopting theIPS (In-plane Switching) mode, which is used to increase viewing anglecharacteristics in liquid crystal displays of the transmission type, toa liquid crystal display of the transflective type.

[0397] Conventionally, the IPS mode has been used for liquid crystaldisplays of the transmission type. However, since the directorconfiguration of the liquid crystal is not changed sufficiently for thetransmission display on the comb-shaped electrode used in the IPS mode,the director configuration of the liquid crystal on the comb-shapedelectrode does not contribute to the display, thereby failing to realizesatisfactory display. In the present example, however, regions on thecomb-shaped line, which could not be used in the conventional IPSsystem, are used to realize the reflection display, thereby making itpossible to provide a liquid crystal display of the transflective typewith high light efficiency.

[0398]FIG. 21(a) is a cross section of a major portion of the liquidcrystal display of the present example when no voltage is applied, andFIG. 21(b) is a cross section of the major portion of the liquid crystaldisplay of FIG. 21(a) when a voltage is applied. Both of FIGS. 21(a) and21(b) are the cross sections when the liquid crystal cell of the presentliquid crystal display is cut at a plane perpendicular to theorientation along which the electrode line (terminal) of the comb-shapedelectrode provided in the liquid crystal cell extends.

[0399] In the liquid crystal display shown in FIGS. 21(a) and 21(b), theliquid crystal layer 1 is sandwiched by a light transmitting substrate51 and a substrate 54, which is given light reflecting properties bybeing provided with a light reflecting comb-shaped electrode 53 (displaycontent overwriting means, voltage applying means, alignment mechanism).Further, the phase difference compensation plate 16 and polarizationplate 14 are provided to the outside of the substrate 51 (the oppositeside from the surface facing the substrate 54), and the phase differencecompensation plate 17 and polarization plate 15 are provided to theoutside of the substrate 54 (the opposite side from the surface facingthe substrate 51). Herein, the phase difference compensation plate 16 iscomposed of a single phase difference compensation plate 16, and thephase difference compensation plate 17 is composed of two phasedifference compensation plates.

[0400] The liquid crystal display of the present example is alsoarranged in the following manner. That is, on the substrate 54(electrode substrate), one of the pair of substrates sandwiching theliquid crystal layer 1, an insulation film 11 (alignment mechanism) ispatterned on a glass substrate 52 by spin-coating an insulationphoto-sensitive resin, irradiating the UV rays with masking, so as toleave no photo-sensitive resin in the transmission display section 10,while forming a layer of the photo-sensitive resin of a predeterminedthickness in the reflection display section 9. Consequently, the liquidcrystal layer 1 is made thinner in the transmission display section 10than in the reflection display section 9.

[0401] In the liquid crystal display of the present example, the lightreflecting comb-shaped electrode 53 (alignment mechanism) is formed onthe glass substrate 52 to cover the insulation film 11. The comb-shapedelectrode 53 is a reflective pixel electrode serving both as the liquidcrystal driving electrode for driving the liquid crystal layer 1 and thereflection film (reflecting means), and it is made of metal having highlight reflectance.

[0402] In the present liquid crystal display, the director configurationof liquid crystal molecules 1 a is changed by the electric field appliedthereon by the comb-shaped electrode 53 in the transmission displaysection 10. In the reflection display section 9, the liquid crystallayer 1 is driven by the electric field generated by the comb-shapedelectrode 53, and the reflecting function of the comb-shaped electrode53 is used for the display.

[0403] In the present example, the line of the comb-shaped electrode 53is used as the reflecting means. However, projections and depressionsmay be provided to the surface thereof, or a light scattering film maybe additionally formed on a region opposing the comb-shaped electrode 53at the outside of the glass substrate 51 to confer light scatteringproperties to the comb-shaped electrode 53.

[0404] In the liquid crystal display of FIGS. 21(a) and 21(b), differentpotentials are given to the adjacent comb-shaped electrodes 53 a and 53b, whereby an electric field develops between the comb-shaped electrodes53 a and 53 b. As shown in FIG. 21(b), the transmission display section10 corresponds to a space between the comb-shaped electrodes 53 a and 53b, and the director configuration of the liquid crystal at thisparticular portion is changed drastically by the pair of comb-shapedelectrodes (comb-shaped electrodes 53 a and 53 b) while keeping itsorientation in parallel with the glass substrate 52. In addition, thereflection display section 9 corresponds to a portion directly above thecomb-shaped electrode 53 (comb-shaped electrodes 53 a and 53 b). In thisparticular portion, the director configuration of the liquid crystaldisplay changes not only in the orientation along the plane of the glasssubstrate 52, but also the orientation perpendicular to the glasssubstrate 52. This is because, as shown in FIG. 21(b), the lines ofelectric force (indicated by broken lines in the drawing) extendsubstantially in parallel with the glass substrate 52 in thetransmission display section 10, while in the reflection display section9, the lines of electric force have components which are perpendicularto the glass substrate 52.

[0405] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal) in the reflection displaysection 9 and transmission display section 10 in the liquid crystaldisplay of the present example is set forth in Table 7 below for readycomparison with reference to a common orientation.

[0406] The optical shown in Table 7 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and each phase difference compensation plate forming the phasedifference compensation plate 17 is set forth in accordance with theactual position from the viewer's side.

[0407] The direction of director of the liquid crystal layer 1 (thealignment orientation of the major axis of the liquid crystal moleculesla) on the substrate 51 side is identical with the orientation of therubbing treatment applied to the surface thereof, and the alignmentorientation on the substrate 54 side is identical with the orientationof the rubbing treatment applied to the surface thereof. Hereinafter,the alignment orientation of the liquid crystal layer 1 on the substrate51 side is referred to as the substrate 51 alignment orientation, andthe direction of director of the liquid crystal layer 1 on the substrate54 side is referred to as the substrate 54 alignment orientation.

[0408] In Table 7 below, each orientation is expressed in degrees fromthe reference orientation set arbitrarily on the display surface, andthe retardation of each phase difference compensation plate is expressedin nm with respect to a beam of monochrome light having the wavelengthof 550 nm.

[0409] Here, the direction, along which the electrode line (terminal) ofthe comb-shaped electrode 53 extends, forms an angle of 65° with respectto the reference orientation, and the director configuration of theliquid crystal molecules 1 a initially aligned at an angle of 75° bothin the reflection display section 9 and transmission display section 10is re-aligned at a greater angle. In addition, in the present liquidcrystal display, Δn·d of the liquid crystal layer 1 is set to about 130nm in the reflection display section 9 and about 240 nm in thetransmission display section 10. TABLE 7 EXAMPLE 12 SEC. 9 SEC. 10 PLATE14 TRANSMISSION AXIS 0 ORIENTATION (°) PLATE PLATE SLOW AXIS ORIENTATION(°) 15 16 RETARDATION (nm) 270 LC LAYER 1 SUBSTRATE 51 75 75 ALIGNNENTORIENTATION (°) SUBSTRATE 54 75 75 ALIGNMENT ORIENTATION (°) PLATE PLATESLOW AXIS ORIENTATION (°) −15 17 RETARDATION (nm) 240 PLATE SLOW AXISORIENTATION (°) −75 RETARDATION (nm) 270 PLATE 15 TRANSMISSION AXIS 90ORIENTATION (°)

[0410] In the liquid crystal display set as above, both the reflectiondisplay section 9 and transmission display section 10 show the darkdisplay when no voltage is applied to the liquid crystal layer 1. If avoltage is applied to the liquid crystal layer 1 under these conditions,the liquid crystal molecules 1 a change their director directions todeviate from the orientation (herein, 65° orientation) along which theelectrode line (terminal) of the comb-shaped electrode 53 extends. Thus,the present liquid crystal display can realize the light display bychanging the director configuration of the liquid crystal with anincreasing applied voltage.

[0411] The display characteristics of the liquid crystal display ofExample 12 assembled in the above manner are graphed in FIG. 22. Thedisplay characteristics of FIG. 22 were measured in the same manner asExample 1, and in the drawing, the horizontal axis represents a rootmean square value of the applied voltage and the vertical axisrepresents the brightness (reflectance or transmittance).

[0412] In FIG. 22, a curve 351 indicates the voltage dependence of thereflectance of the reflection display section 9, and a curve 352indicates the voltage dependence of the transmittance of thetransmission display section 10 in the liquid crystal display of Example12. Although the optical characteristics differ in the reflectiondisplay section 9 depending on the position on the comb-shaped electrode53, the optical characteristics of the most typical portion are setforth in FIG. 22.

[0413] As can be understood from FIG. 22, the liquid crystal display ofExample 12 shows the dark display both in the reflection display section9 and transmission display section 10 when no voltage is applied, andboth the reflectance and transmittance increase with an increasingapplied voltage. That is, when the applied voltage is 2V, both thereflectance of the reflection display section 9 and the transmittance ofthe transmission display section 10 are 3%, and when the applied voltageis increased to 5V, both increase to 35° and 38%, respectively. Thus,the above liquid crystal display can attain satisfactory brightness andcontrast ratio for the light display both in the reflection displaysection 9 and transmission display section 10, thereby realizing thedisplay with excellent visibility. Also, since the contrast ratio ishigher in the transmission display section 10 than in the reflectiondisplay section 9, the above liquid crystal display can further improvethe display quality and show more satisfactory display.

[0414] As has been explained, according to Example 12, it was confirmedthat there can be provided a liquid crystal display of the transflectivetype which can realize the reflection display on the region above thecomb-shaped line 53, which could not be used for the display in theconventional IPS system, while attaining high light utilization.

[0415] In the present embodiment, besides the method using the nematicliquid crystal in the aforementioned IPS mode, a method using theferroelectric liquid crystal display mode or a method using theanti-ferroelectric liquid crystal display mode can be adopted as amethod for realizing the above-described director configuration of theliquid crystal.

[0416] In Example 13 below, a liquid crystal display using theferroelectric liquid crystal display mode will be explained as anotherexample liquid crystal display for realizing the above-describeddirector configuration of the liquid crystal.

EXAMPLE 13

[0417] In the present example, a liquid crystal cell is produced in thesame manner as its counterpart used for assembling the liquid crystaldisplay of Example 1 except that:

[0418] surface-stabilized ferroelectric liquid crystal is used as aliquid crystal material;

[0419] the thicknesses (d) of the liquid crystal layer 1 in thetransmission display section 10 and reflection display section 9 are setto 1.4 μm and 0.7 μm, respectively;

[0420] Δn·d of the liquid crystal layer 1 in the reflection displaysection 9 and transmission display section 10 are set to 130 nm and 260nm, respectively; and

[0421] a reflective electrode is used for a region corresponding to thereflection display section 9 instead of forming the reflection film 8over the electrode 7 for the reflection display section 9.

[0422] To be more specific, the insulation film 11 is patterned over thesubstrate 5 (glass substrate) in such a manner that no photosensitiveresin is left in the transmission display section 10, while a 0.7μm-thick layer of the photosensitive resin is formed in the reflectiondisplay section 9. Also, a reflective electrode is formed where theinsulation film 11 is formed (reflection display section 9), and atransparent electrode is formed where the insulation film 11 is notprovided (transmission display section 10). Then, the alignment film 3is formed on the substrate 5 on the surface on which is formed theelectrode, to which the alignment treatment is applied by means ofrubbing, whereby the electrode substrate is produced. The otherelectrode substrate (opposing substrate) placed in an opposing positionto the electrode substrate thus obtained is arranged in the same manneras its counterpart in Example 1. Then, the liquid crystal cell isproduced by filling a space between the two electrode substrates withferroelectric liquid crystal composition containing thesurface-stabilizing ferroelectric liquid crystal. Subsequently, theliquid crystal display is assembled by laminating the phase differencecompensation plates 16 and 17 and the polarization plates 14 and 15 tothe outside of the respective electrode substrates forming the liquidcrystal cell. Herein, the phase difference compensation plate 16 iscomposed of a single phase difference compensation plate, and the phasedifference compensation plate 17 is composed of two phase differencecompensation plates.

[0423] The optical of the polarization plates 14 and 15, phasedifference compensation plates 16 and 17, and the liquid crystal layer 1(that is, the lamination orientation of the polarization plates 14 and15, and phase difference compensation plates 16 and 17, and thealignment orientation of the liquid crystal of dark display and lightdisplay) in the liquid crystal display of the present example is setforth in Table 8 below for ready comparison with reference to a commonorientation.

[0424] The optical shown in Table 8 is the position of each opticalelement on the display surface when the viewer observes the displaysurface, and each phase difference compensation plate forming the phasedifference compensation plate 17 is set forth in accordance with theactual position from the viewer's side. Also, in Table 8, eachorientation is expressed in degrees from the reference orientation setarbitrarily on the display surface, and the retardation of each phasedifference compensation plate is expressed in nm with respect to a beamof monochrome light having the wavelength of 550 nm. TABLE 8 EXAMPLE 13SEC. 9 SEC. 10 PLATE 14 TRANSMISSION AXIS 0 ORIENTATION (°) PLATE PLATESLOW AXIS ORIENTATION (°) 15 16 RETARDATION (nm) 270 LC LAYER 1SUBSTRATE 51 D:75  ALIGNMENT ORIENTATION (°) L:120 SUBSTRATE 54 D:75ALIGNMENT ORIENTATION (°) L:120 PLATE PLATE SLOW AXIS ORIENTATION (°)−15 17 RETARDATION (nm) 270 PLATE SLOW AXIS ORIENTATION (°) −75RETARDATION (nm) 270 PLATE 15 TRANSMISSION AXIS 90 ORIENTATION (°)

[0425] The liquid crystal display assembled in the above manner canattain satisfactory brightness and contrast ratio both in the reflectiondisplay section 9 and transmission display section 10.

[0426] As has been explained, any type of liquid crystal display whichcan realize different director configurations of the liquid crystal anddifferent thicknesses of the liquid crystal layer in the reflectiondisplay section 9 and transmission display section 10 simultaneously canserve as the liquid crystal display of the transflective type of thepresent invention and show satisfactory display even if the alignmentdirection of the liquid crystal layer 1 changes in the plane of theliquid crystal layer upon the voltage application. In case that theliquid crystal display adopts the IPS mode, the light efficiency can beimproved compared with the conventional liquid crystal display of thetransmission type also adopting the IPS mode. In addition, the liquidcrystal display of the present embodiment can be used in the other modesusing the ferroelectric liquid crystal and the like.

Embodiment 7

[0427] In the present embodiment, a specific example of an elementsubstrate and a color filter substrate driven by an active matrix, whichrealize the arrangement of the liquid crystal display of the presentinvention, will be explained.

[0428] In assembling the liquid crystal display of the present inventionaiming at displaying an image, it is very critical to set a ratio of thetransmission display section and reflection display section based on howfrequently the liquid crystal display is mainly used for thetransmission display and reflection display.

[0429] To be more specific, in a first style, like the liquid crystaldisplay of the transmission type currently used, the transmitted lightfrom the lighting device (back light) serving as the back lighting meansis mainly used for the display, and the reflection display section isused to prevent the wash-out (this style is referred to as thetransmission-main transflective type, hereinafter).

[0430] In a second style, the reflection display is mainly used for thedisplay, in which the power-consuming back light is turned ON/OFFfrequently depending on the circumstances to save the power consumption,and therefore, the back light is turned ON only when the ambient lightis so weak that the display content can not be seen by the reflectiondisplay alone (this style is referred to as the reflection-maintransflective type, hereinafter).

[0431] The above two styles are distinguished from each other based onwhether the display is chiefly shown by the transmission display orreflection display, and for this reason, a specific area ratio of thetransmission display section and reflection display section, a color ofthe color filter in case of color display, etc. must be designeddifferently in each style.

[0432] Thus, in the first place, a liquid crystal display using fordisplay TFT elements as adopting one of the active matrix methods willbe explained as an example of the liquid crystal display of thetransmission-main transflective type. Hereinafter, like components arelabeled with like reference numerals with respect to Embodiments 1through 6, and, for ease of explanation, the description of thesecomponents is not repeated here.

[0433] To begin with, the arrangement of the substrate in the liquidcrystal display of the transmission-main transflective type using theTFT elements for the display will be explained with reference to FIGS.23(a) through 25.

[0434]FIG. 23(a) is a plan view illustrating a major portion of the TFTelement substrate for realizing the liquid crystal display of thetransmission-main semi-transmission type of present embodiment. FIG.23(b) is a view showing a driving electrode 19 for the reflectiondisplay section 9 (see FIGS. 1, 4, 24, and 25) on the TFT elementsubstrate of FIG. 23(a). FIG. 23(c) is a view showing a transparentpixel electrode 20 on the TFT element substrate of FIG. 23(a).

[0435]FIG. 24 is a cross section of the TFT element substrate sliced online A-A′ of FIG. 23(a). To be more specific, FIG. 24 is a cross sectionof the TFT element substrate traversing the TFT element 21 to thedriving electrode 19 and transparent pixel electrode 20 and further to astorage capacitor section 26. FIG. 25 is a cross section of the TFTelement substrate of FIG. 23(a) sliced on line B-B′ of FIG. 23(a), andshows the arrangement on the cross section at a boundary portion ofadjacent pixels.

[0436] As shown in FIGS. 23(a), 24, and 25, a pixel electrode 18 drivingthe liquid crystal layer 1 (see FIGS. 1 and 4) is composed of thedriving electrode 19 (display content overwriting means, voltageapplying means) in the reflection display section 9 and the transparentpixel electrode 20 (display content overwriting means, voltage applyingmeans) made of ITO. The driving electrode 19 may be a reflectiveelectrode rendering the reflecting properties. Also, the drivingelectrode 19 and transparent pixel electrode 20 may be electricallyconnected to each other when adopting a display method in which thedisplay is not inverted when the displays are shown on the same voltage.

[0437] The driving electrode 19 and transparent pixel electrode 20 areconnected to a drain terminal 22 of the TFT element 21 which controls avoltage applied to each pixel for the display. In case that the drivingelectrode 19 is a reflective electrode and furnished with a transmissiondisplay opening 19 a, a region where the transmission display opening 19a is made through is used for the transmission display as thetransmission display section 10.

[0438] On the layer beneath the driving electrode 19, the TFT element21, lines 23 and 24, storage capacitor section 26 and a storagecapacitor line 27 are provided. Note that, however, since thesecomponents are made of light-blocking material, such as metal, the TFTelement substrate is produced in such a manner that none of thesecomponents is provided in the transmission display opening 19 a. In FIG.23(a), the driving electrode 19 is indicated by a two-dot chain line.

[0439] Also, as shown in FIG. 24, a major portion of the drivingelectrode 19 of the reflection display section 9 for applying a voltageto the reflection display section 9 forming the driving electrode 18 isspaced apart from the surface of the substrate 19 on which are formedthe lines 23 and 24 for driving the TFT element 21 and the TFT element21 (TFT element substrate surface) by an organic insulation film 25. Theorganic insulation film 25 is made of an organic insulation materialhaving a low dielectric constant so as to have a layer thickness of 3 μmfor the following reasons:

[0440] to prevent a parasitic capacitor component, formed between thepixel electrode 18 and the line 23 which will be used as the gate lineof the TFT element 21 or the line 24 which will be used as the sourceline of the TFT element 21, from delaying or deforming a gate signalwaveform or a source signal waveform which controls the opening/closingaction of the TFT element 21, so that a high-resolution dot matrixdisplay is shown; and

[0441] to improve the optical characteristics of the reflection displaysection 9 and transmission display section 10 in the liquid crystaldisplay of the present embodiment.

[0442] The pixel electrode 18 is connected to the drain terminal 22 ofthe TFT element 21. The drain terminal 22 is an n⁺ amorphous siliconlayer doped to form the n type semiconductor, and serves as the drainelectrode of the TFT element 21. In the TFT element substrate of thepresent embodiment, the ITO layer placed to touch the drain terminal 22is used as the transparent pixel electrode 20, and the driving electrode19 of the reflection display section 9 is formed on the organicinsulation film 25 which is patterned in such a manner as to cover thetransparent pixel electrode 20 partially. In other words, in the liquidcrystal display of the transmission-main transflective type using theTFT element substrate of FIG. 24, the transparent pixel electrode 20used for the transmission display and the driving electrode 19 used forthe reflection display are electrically connected at the patternboundary of the organic insulation film 25. Further, smooth protrusionand depressions may be provided on the surface of the driving electrode19 of the reflection display section 9 as shown in FIGS. 24 and 25 toprevent the surface from turning into a specular reflector.

[0443] Also, as shown in FIG. 25, the organic insulation film 25 isformed to cover the line 24 connected to the source terminal 28 of theTFT element 21 at the boundary of adjacent pixels on the TFT elementsubstrate, whereby the driving electrode 19 of the reflection displaysection 9 is formed on the organic insulation film 25.

[0444] The TFT element substrate produced in this manner can control theparasitic capacitor component produced by the pixel electrode 18 andlines 23 and 24 through the organic insulation film 25 by setting anappropriate relation between the layer thickness and dielectric constantof the organic insulation film 25. Thus, as shown in FIG. 23(a), thedriving electrode 19 of the reflection display section 9 can be extendeddirectly above the lines 23 and 24. In this case, a space between theadjacent pixel electrodes 18 can be narrowed, and the leaking electricfield from the lines 23 and 24 to the liquid crystal layer 1 throughsuch a space can be reduced. Consequently, the director configuration ofthe liquid crystal layer 1 is hardly disturbed. Thus, the directorconfiguration of the liquid crystal in the liquid crystal layer 1 can becontrolled closer to the boundary between adjacent pixel electrodes 18by setting an adequate relation between the layer thickness anddielectric constant of the organic insulation film 25. Hence, there canbe produced a TFT element substrate for the liquid crystal display ofthe transmission-main transflective type having a high aperture. In thepresent embodiment, the organic insulation film 25 is made of an organicinsulation material having a relative dielectric constant of 3.5 to havea film thickness of 3 μm.

[0445] As has been explained, in the present embodiment, the TFT elementsubstrate, in which 45% of the entire pixel area is used for thetransmission display, and 38% of the same is used for the reflectiondisplay, is produced. Given that the most general conventional TFTliquid crystal display of the transmission type attains an aperture ofabout 50% in the transmission display section, the present TFT elementsubstrate can be said to be the TFT element substrate for a liquidcrystal display of the transmission-main transflective type with highlight efficiency, because it secures a ratio for the area of thetransmission display section 10 which is substantially the same as inconventional displays, and also shows display by adding the luminance ofthe display light in the reflection display section 9 to thetransmission display light.

[0446] The reason why the liquid crystal display of the presentembodiment can attain high light utilization is because the lightblocking components, such as TFT elements 21, lines 23 and 24, storagecapacitor 26, and storage capacitor line 27, are provided to thereflection display section 9, and thus these components do not cause anyloss of the light used for the liquid crystal display.

[0447] Next, the color filter substrate placed to oppose the TFT elementsubstrate produced in the above manner will be explained with referenceto FIGS. 26(a) and 26(b).

[0448] As shown in FIGS. 26(a) and 26(b), three color filters, namely, acolor filter 61R for red (R), a color filter 61G for green (G), and acolor filter 61B for blue (B), are formed on the color filter substrate.Each of the three color filters 61R, 61G, and 61B is made ofphotosensitive resin in which a pigment is dispersed, and formedseparately on the glass substrate 62 as a planar and stripe color layerin a matching position with the pixels on the TFT element substrate.

[0449] Further, as shown in FIG. 26(b), a smoothing layer 501 made oftransparent acrylic resin is formed on the glass substrate 62 on thesurface where the color filters 61R, 61G, and 61B are formed to coverthe same. Also, a 140 nm-thick ITO film is sputtered on the smoothinglayer 501, using a blocking mask covering non-specified portions, toserve as a counter electrode 502 (display content overwriting means,voltage applying means) for the pixel electrode 18 of the TFT elementsubstrate. Consequently, the color filters 61R, 61G, and 61B areseparated from each other by transparent regions.

[0450] The superimposing position of the color filter substrate and TFTelement substrate is shown in FIG. 26(a). That is, the transmissiondisplay opening 19 a (transmission display section 10) of the drivingelectrode 19 formed in the reflection display section 9 on the TFTelement substrate is completely covered with the stripe color filters61R, 61G, and 61B. On the other hand, only the portion of the drivingelectrode 19 in the reflection display section 9 along the extendingdirection of the color filters 61R, 61G, and 61B is covered with thecolor filters 61R, 61G, and 61B. The transparent regions betweenadjacent color filters 61R, 61G, and 61B are placed to oppose thedriving electrode 19 formed in the reflection display section 9 at theother portion (the portion other than the one along extending directionof the color filters 61R, 61G, and 61B).

[0451]FIG. 27 shows the positions of the reflection display section 9,transmission display section 10, color filters 61R, 61G, and 61B by wayof a combination of the color filter substrate and TFT elementsubstrate. FIG. 27 is a cross section of a major portion of the liquidcrystal display sliced on line C-C′ of FIG. 26(a), that is, the crosssection cut along the line C-C′ of the color filter substrate and TFTelement substrate superimposed for the use of the liquid crystaldisplay.

[0452] Thus, any of the color filters 61R, 61G, and 61B is formed in thetransmission display section 10, and the portion of the reflectiondisplay section 9 other than the one along the extending direction ofthe color filters 61R, 61G, and 61B corresponds to the transparentregions among the color filters 61R, 61G, and 61B.

[0453] According to the above arrangement, the color filters 61R, 61G,and 61B of the same kind as those used for the transmission displayfunction only on a part of the reflection display section 9.Consequently, the color display can be realized in the reflectiondisplay, and reflectance necessary for the refection display section canalso be secured.

[0454] The transmission colors shown by the light having passed throughthe color filter substrate produced as shown in FIGS. 26(a) and 26(b)may be the same transmission colors of RGB used for liquid crystaldisplays of the transmission type for each of the RGB pixels, or may beadjusted in an adequate manner, as the case may be.

[0455] In a combination of the TFT element substrate and color filtersubstrate shown in FIGS. 26(a) and 27, the transmission display section10 shows the display using only the light having passed through thecolor filters 61R, 61G, and 61B, and part of the reflection displaysection 9 shows the display using the color filters 61R, 61G, and 61Bused for the transmission display section 10, and the rest shows thedisplay without using the color filters 61R, 61G, and 61B. This isbecause the reflection display section 9 can not attain sufficientbrightness if it uses the color filters 61R, 61G, and 61B entirely, andthe brightness is compensated by providing therein a portion where thecolor filters 61R, 61G, and 61B are not used.

[0456] Further, in the present embodiment, since the display lightpasses through the color filters 61R, 61G, and 61B twice in thereflection display section 9, color filters 61R, 61G, and 61B may beused in the reflection display section 9 which have higher brightnessthan those used in the transmission display section 10.

[0457] Also, as in the present embodiment, the color filters 61R, 61G,and 61B may be provided at least to the transmission display section 10,and the reflection display section 9 may have a region (portion) whereno color filters 61R, 61G, and 61B are provided. Further, the colorfilters 61R, 61G, and 61B may be provided to the transmission displaysection 10 alone, and not to the reflection display section 9.

[0458] In case that color filters 61R, 61G, and 61B are not provided tothe reflection display section 9, a display voltage signal necessary forthe transmission display is a signal suitable for a color display, and adisplay voltage signal necessary for the reflection display is a signalsuitable for a monochrome display. For this reason, there arises adriving problem that the percentage of the contribution of each of theRGB pixels to the brightness is proportional to the luminoustransmittance (Y value) of each color in the transmission displaysection 10, but the percentage in each pixel is the same in thereflection display section 9.

[0459] To be more specific, if the display brightness in a case wherethe B pixels alone show light display is compared to the displaybrightness in a case where the G pixels alone show light display, thebrightness in each pixel, in which the luminous transmittance isconcerned, varies in the transmission display section 10 where the colorfilters 61R, 61G, and 61B are provided, but is the same in thereflection display section 9 where the color filters 61R, 61G, and 61Bare not provided.

[0460] This problem can be eliminated by changing the area of theportion of the reflection display section 9 in each of the RGB pixelsthat does not show the color display in accordance with the Y value foreach of the RGB colors of the color filters 61R, 61G, and 61B used forthe transmission display. Accordingly, the contribution of themonochrome display of the reflection display section 9 to the brightnessin each of the RGB pixels can be adjusted by changing the respectiveareas of the reflection display section 9 in each RGB pixel and thebrightness of the monochrome display based on the area of the reflectiondisplay section 9 can be reflected in the display luminance of eachcolor.

[0461] In addition, the same effect can be obtained by setting the ratioof coverage of the reflection display section 9 by the color filter to adifferent value for each color, in the order G, R, B from smallest tolargest. This method has another advantage that the slight greencoloring occurred when a normal polarization plate is used can becompensated. Also, in case that the color filter substrate and TFTelement substrate are superimposed as shown in FIG. 26(a), a relativelylarge allowance can be secured in the accuracy of the superimposingposition. The reason why is because each pixel exists between portionswhere no color filter is formed in the reflection display section 9, ifan area of one of those portions increases by the position shift, theother decreases accordingly.

[0462] When the TFT element substrate and color filter substratedescribed as above are used, transmission display as good as thetransmission display shown in conventional TFT liquid crystal displayscan be displayed with the use of the lighting device (back light) as theback light means. Further, even when the ambient light is too bright,the display content can be seen because the reflected light is used todisplay the display content very close to the display content in thetransmission display. Hence, there can be realized a high-resolutioncolor liquid crystal display which does not cause parallax and does notwash out even when used with too bright ambient light.

[0463] Next, the arrangement of the substrate of the liquid crystaldisplay of the reflection-main transflective type will be explained withreference to FIGS. 28, 29(a) and 29(b). In the liquid crystal display ofthis type, the arrangements of the TFT element display and color filtersubstrate are changed, so that it is mainly used as a low powerconsuming liquid crystal display which uses the reflected light of theambient light for the display, and shows the transmission display whenthe ambient light is not sufficiently strong.

[0464]FIG. 28 is a plan view showing a major portion of the TFT elementsubstrate for realizing a liquid crystal display of the reflection-maintransflective type of Embodiment 7, and it shows the TFT elementsubstrate which mainly reflects light. In the drawing, the drivingelectrode 19 is represented by a two-dot line.

[0465] As shown in FIG. 28, the liquid crystal display of thereflection-main transflective type is arranged in the same manner as theabove liquid crystal display of the transmission-main transflective typeexcept that the transmission display opening 19 a of the drivingelectrode 19 and the transparent pixel electrode 20 are made smallerthan their respective counterparts on the TFT element substrate used inthe liquid crystal display of the transmission-main transflective type.

[0466] In other words, in the liquid crystal display of thereflection-main transflective type, as shown in FIG. 28, the pixelelectrode 18 which drives the liquid crystal layer 1 (FIGS. 1 and 4) iscomposed of the driving electrode 19 and the transparent pixel electrode20 made of ITO in the reflection display section 9, and the drivingelectrode 19 and transparent pixel electrode 20 are connected to thedrain terminal 22 of the TFT element 21 which controls a voltage appliedto each pixel for the display. Also, the driving electrode 19 isfurnished with the transmission display opening 19 a, and in case thatthe driving electrode 19 is the reflective electrode, a region where thetransmission display opening 19 a is made through is used for thetransmission display as the transmission display section 10 (FIGS. 24,25, and 27).

[0467] Also, the TFT element 21, lines 23 and 24, storage capacitorsection 26, and storage capacitor line 27 are provided on the layerbeneath the driving electrode 19, and these components are providedoutside of the transmission display opening 19 a.

[0468] Note that, however, the TFT element substrate of FIG. 28 isarranged in such a manner that the transmission display section 10 issmaller and the reflection display section 9 (FIGS. 24, 25, and 27) islarger compared with those in the TFT element substrate used in theliquid crystal of the transmission-main transflective type.

[0469] In this manner, in the present embodiment, the TFT elementsubstrate using 13% of the entire pixel area for the transmissiondisplay and 70% of the entire pixel area for the reflection display isproduced as the TFT element substrate for the liquid crystal display ofthe reflection-main transflective type.

[0470] Compared with the ratio of the transmission display section 10 inthe TFT element substrate of the liquid crystal display of thetransmission-main transflective type, 13% is a relatively small valuefor the ratio of the transmission display section 10 in the TFT elementsubstrate for the liquid crystal display of the reflection-maintransflective type. However, in case of the liquid crystal display ofthe reflection-main transflective type using the TFT element substrate,if the transmission display is shown only when the display content cannot be seen with reflection display alone, the ON time of the lightingdevice (back light) as the back light means is controlled. Consequently,the power consumption can be saved, thereby proving of the practical useof the present liquid crystal display.

[0471] Next, the following will explain the arrangement of the colorfilter substrate used in a combination with the TFT element substratewith reference to FIGS. 29(a) and 29(b).

[0472] As shown in these drawings, the color filter 61R for red (R),color filter 61G for green (G), and color filter 61B for blue (B) areprovided on the glass substrate 62 in stripes in the same manner as thecolor filter substrate for the liquid crystal display of thetransmission-main transflective type of FIGS. 26(a) and 26(b). Asmoothing layer 501 made of transparent acrylic resin is formed on theglass substrate 62 on the surface where the color filters 61R, 61G, and61B are formed to cover the same. Also, a ITO film is sputtered on thesmoothing layer 501, using a blocking mask covering non-specifiedportions, to serve as a counter electrode 502 for the pixel electrode 18of the TFT element substrate.

[0473] Note that, however, the color filter substrate for the liquidcrystal display of the reflection-main transflective type of FIGS. 29(a)and 29(b) is different from the one used for the liquid crystal displayof the transmission-main transflective type of FIGS. 26(a) and 26(b) inplanar shapes and spectral transmittance in each color.

[0474] To be more specific, on the color filter substrate of the liquidcrystal display of the reflection-main transflective type,. the colorfilters 61R, 61G, and 61B (color layer) are formed to cover thereflection display section 9 on the TFT element substrate entirely, andthese color filters 61R, 61G, and 61B are made to attain high brightnessto allow the display light to attain satisfactory brightness afterhaving passed through the color filters 61R, 61G, and 61B twice, becausethe display light passes through the color filters 61R, 61G, and 61Btwice in the reflection display section 9.

[0475] For this reason, satisfactory reflection display can be shown inthe reflection display section 9 by means of a combination of a TFTelement substrate having the reflection display section 9 in a largeratio, and a corresponding color filter substrate suited to reflectiondisplay.

[0476] Further, in the transmission display section 10, the transmissiondisplay opening 19 a is small, but the display content can also be seenduring the transmission display, which is used only when the ambientlight is not sufficiently strong by suing the lighting device (backlight) as the back lighting means. This is the difference thatdistinguishes the liquid crystal display of the reflection-maintransflective type of the present embodiment from a conventional liquidcrystal display of the reflection type. With the liquid crystal displayof the reflection-main transflective type of the present embodiment,when the transmission display is shown by the color filters 61R, 61G,and 61B adjusted suitably for the reflection display, the chroma is notsatisfactory but the display colors can be confirmed.

[0477] Thus, in case that the above liquid crystal display of thereflection-main transflective type shows the color display, it iseffective to use an arrangement whereby the color filters 61R, 61G, and61B are provided to the reflection display section 9 to show the colordisplay, and in the transmission display section 10, either the colorfilters 61R, 61G, and 61B are not provided or color filters 61R, 61G,and 61B having chroma at least as good as the chroma of those providedto the reflection display section 9 are provided partially.

[0478] As has been discussed, the liquid crystal display of thereflection-main transflective type can be arranged in such a manner thatthe color filters 61R, 61G, and 61B are provided at least to thereflection display section 9, and the transmission display section 10has a portion where the color filters 61R, 61G, and 61B are notprovided, or the color filters 61R, 61G, and 61B are not provided to thetransmission display section 10, so that it shows the monochromedisplay. In the latter case, the transmission display section 10 can bemade smaller because the light transmittance increases. Consequently, alarger area can be secured as the reflection display section 9, and moresatisfactory display can be obtained in the normal reflection display.

[0479] In this case, like in the liquid crystal display of thetransmission-main transflective type, the area of the portion of thedisplay section where the color display is not shown, that is, the areaof the portion of the transmission display section 10 that does not showthe color display, may be changed for each of the RGB pixels inaccordance with the Y value of each color of the color filters 61R, 61G,and 61B. In other words, each substrate may be produced in such a mannerthat the ratio of the transmission display area for each of the RGBpixels is changed, so that the contribution of monochrome display of thetransmission display section 10 to the brightness in each of the RGBpixels is set adequately by taking the luminous transmittance intoconsideration.

[0480] On the other hand, although the power consumption increases forturning ON the lighting device (back light) as the back light means,vivid color filters suitable for the transmission display in thetransmission display section 10 can be used by brightening the lightemanated from the lighting device (back light) sufficiently. In thiscase, not only the chroma, but also the color reproduction of thetransmitted light can be secured. In any case, it is very important tokeep the lighting device (back light) turned OFF as much as possible tosave the power consumption.

[0481] As has been explained, according to the present embodiment, ithas become possible to provide a liquid crystal display of thereflection-main transflective type which can save the power consumptionduring normal use, and prevent wash-out in the reflection displaysection 9, while showing the transmission display using the back lightmeans (back light) when occasion demands.

[0482] In the above explanation, the TFT element 21 is used as theswitching element in the active matrix method, and an amorphous siliconTFT element of the bottom gate type is used as an example of the TFTelement 21. However, the switching element of the present embodiment isnot limited to the above disclosure, and may be a polysilicon TFTelement, or an MIM (Metal Insulator Metal) element known as a 2-terminalelement, for example. Also, it should be appreciated that these activeelements are not necessarily used, and can be omitted, as the case maybe.

[0483] As has been explained, in each liquid crystal display of thepresent embodiment, the thickness of the liquid crystal layer can bechanged in the reflection display section 9 and transmission displaysection 10 by a film thickness of the organic insulation film 25 byemploying the TFT element substrate, in which the driving electrode 19serving as the display electrode is separated from the lines 23 and 24by the organic insulation film 25. Moreover, in each liquid crystaldisplay of the present embodiment, even when a thickness of the organicinsulation film 25 is as thin as 3 μm (at which a high capacitor displayis allowed based on the line resistance and parasitic capacitor of theTFT element substrate), a difference in liquid crystal layer thicknesssufficient to realize satisfactory display on both the reflectiondisplay section 9 and transmission display section 10 (as has beendiscussed Embodiments 1 and 2) can be secured.

[0484] Thus, a liquid crystal display capable of showing high capacitordisplay can be provided by employing the TFT element substrate arrangedin the manner illustrated in FIG. 23(a) or 28 and adopting the liquidcrystal display method described in Embodiment 1 or 2.

[0485] Further, since the TFT element substrate using theabove-mentioned organic insulation film 25 has been applied in part tothe liquid crystal displays for the transmission display alone adoptingthe normal TFT element driving method, the above TFT element substratehas fewer technical problems for the mass production, thereby proving ofits high probabilities for the practical application.

[0486] The inventors of the present invention have been carrying out anassiduous study on the production of a reflection film renderingsatisfactory reflection properties by smooth protrusion and depressionsprovided thereon to prevent the display surface from turning into aspecular reflector in the liquid crystal display of the reflection type.They discovered that a similar surface with the protrusion anddepressions can be formed on the organic insulation film 25 used in thepresent invention. Accordingly, the TFT element substrate for the liquidcrystal display of the transmission-main transflective type of FIGS.23(a) through 27 is furnished with the protrusions and depressions in aportion corresponding to the reflection display section 9.

[0487] As has been explained, the present embodiment includes the liquidcrystal display of the transmission-main transflective type and thereflection-main transflective type, and a ratio of the display surfacesof the transmission display section and reflection display section,colors of the color filters in case of color display, etc. are changeddepending on whether the display is mainly shown by the transmissiondisplay or reflection display.

[0488] Next, a ratio of the transmission display section and reflectiondisplay section in the liquid crystal display of the present inventionwill be explained in Embodiment 8 below.

Embodiment 8

[0489] A ratio between the respective areas of the transmission displaysection and reflection display section must be set by taking thevisibility into consideration. Stevens et al. (“Brightness Function:Effect of Adaptation”, Journal of the Optical Society of America, Vol.53, No. 3, page 375) investigates the brightness perceived visually(perceived brightness), giving consideration the adaptation of humanvision. According to this publication, even when a human is seeingobjects with the same luminance, the perceived brightness depends on thebrightness to which he is currently adapted, and there has beenestablished a quantitative relation therebetween.

[0490]FIG. 30 shows a relation of the adapted brightness for providingthe perceived brightness values ranging from 5 brils to 45 brils versusthe sample luminance, which was prepared based on the study of Stevenset al. expressed in different units. In the drawing, the horizontal axisrepresents the adapted luminance (unit: cd/m²) to which a viewer of thesample is adapted, and the vertical axis represents the luminance (unit:cd/m²) of the sample (sample luminance) presented to the viewer.

[0491] In the drawing, a point A represents the perceived brightnesswhen a viewer adapted to the adapted luminance of 1 cd/m² observes asample having a surface at the luminance of 10 cd/m², and a point Brepresents the perceived brightness when a viewer adapted to an adaptedluminance of 1700 cd/m² observes a sample having a surface at theluminance of 300 cd/m². FIG. 30 reveals that, given the fact that theperceived brightness on both the points A and B shows the same value(9.4 brils), the brightness perceived by human is affected not only bythe luminance of the display surface, but also by the adapted luminance.

[0492] Next, the adaptation of the viewer of the display surface of aliquid crystal display will be discussed.

[0493] To begin with, the object to which the viewer adapts will bediscussed. When a human observes a particular object and adapts to itsbrightness, he adapts to the luminance on the surface of the visibleobject in the visual surroundings, which generally varies with thecircumstantial conditions. However, it is very useful to take theadapted object into consideration as a kind of measure, that is, toconsider the situation in which the observed object is assumed to be asurface reflecting the ambient light. This is because whether indoors oroutdoors, a human more often adapts to reflection surfaces illuminatedby a light source than to the light-emitting light source itself. In thefollowing, the adaptation of the viewer who adapts one's vision to theobject's reflection surface will be discussed.

[0494] In this case, the adapted luminance of FIG. 30 is represented bya value obtained by multiplying a predetermined value with theilluminance on the object surface to which the viewer adapts, lighted byan illuminating light source. Let L be the illuminance (unit: lux) and Bbe the luminance (unit: cd/m²), then, the luminance (B) on a surfacehaving a reflectance ratio R in the reference of the perfect reflectingdiffuser surface is computed as: B=L×R/π. Herein, it is appropriate touse a surface of N5 on Munsell color standard known as having averagereflectance for objects generally observed by humans, and to treat theadapted luminance as the luminance of the surface of the N5 on Munsellcolor standard lighted by predetermined illuminance. In this case, R is0.2.

[0495] Further, assume that the illuminance light source lighting thesurface of N5 on Munsell color standard as the representative of theobserved object also lights the surface of a sample object whoseperceived brightness is evaluated under the adapted conditions. By theabove assumption, the perceived brightness of the reflection displaysection when the viewer is observing the liquid crystal display can belinked to the illuminance at which the liquid crystal is lighted throughthe adapted luminance. Consequently, specific reflectance or ratio ofthe area of the reflection display section can be selected based on thedata obtained from the psychophysical experiments.

[0496] As the result of the study of the inventors of the presentinvention, a specific standard for perceived brightness can be expressedas the brightness values set forth in Table 9 below. The inventorsreproduced several combinations of the adapted luminance and sampleluminance, and discovered that the brightness expression set forth inTable 9 below is appropriate. Table 9 can be used as the reference whensetting the reflection display section based on the perceivedbrightness. TABLE 9 PERCEIVED BRIGHTNESS (UNIT: brils) 0 ≦ PB < 5 TOODARK TO SEE  5 ≦ PB < 10 DARK 10 ≦ PB < 20 NORMAL 20 ≦ PB < 30 BRIGHTAND GOOD OBSERVATION 30 ≦ PB TOO BRIGHT

[0497] Here, typical reflectance (R) of the liquid crystal display ofthe reflection type is about 30% in the polarization plate method. Thus,the operation of the liquid crystal display of the transflective type ofthe present invention will be explained using the above specific value.

[0498] A straight line 601 of FIG. 30 indicates the display operation ofthe liquid crystal display having the reflectance of 30%. In otherwords, let L (unit: lux) be the illuminance of the illuminance lightsource lighting the luminance surface to which the viewer adapts, thenthe adapted luminance by the surface of N5 on Munsell color standard iscomputed as 0.2×L/π, because the reflectance (R=20%) of the surface ofN5 on Munsell color standard varies with the luminance (L/π) of theperfect reflecting diffuser surface lighted by the same illuminancelight source. Likewise, the luminance on the display surface of theliquid crystal display (sample object) having the reflectance of 30%when lighted by the same illuminance light source can be computed as:0.3×L/π. In other words, the straight line 601 is obtained by plottingthe varying illuminance (L) on the points which satisfy a relationestablished between the horizontal axis of 0.2 L/π and the vertical axisof 0.3 L/π. As in the case of using the liquid crystal display havingthe reflectance of 30% as the sample object, a straight line 602 isobtained by plotting the varying illuminance (L) on the points whichsatisfy a relation established between the horizontal axis of 0.2 L/πand the vertical axis of 0.1 L/π.

[0499] Next, the usable circumstances of the above liquid crystaldisplay having the reflectance of 30% will be discussed in thefollowing. The adapted luminance by the surface of N5 on Munsell colorstandard at the illuminance (about 100,000 lux) of direct sunlight infair weather, which is the brightest illuminating conditions a human canexperience in normal life, is about 6000 cd/m². Here, as shown in FIG.30, the perceived brightness on the display surface of the liquidcrystal display having the reflectance of 30% is the intersection of thestraight line 602 and a straight line 605 indicating the adaptiveluminance of 6000 cd/m², or approximately 30 brils, which is as shown inTable 9 above, is too bright. For this reason, the perceived brightnessat lower illuminance is below the value of the above perceivedbrightness. Hence, the illuminance capable of securing a perceivedbrightness of 10 brils is about 450 lux (found by calculating backwardfrom the corresponding adapted luminance using the above equation). Inother words, when light display having brightness between 10 brils and30 brils inclusive is necessary, the illuminance is 450 lux at theminimum and 100,000 lux at the maximum. Thus, the above liquid crystaldisplay can be used outdoors during normal day time or in interiorshaving illuminance of 450 lux or above (for example, in a room lightedby a light of 450 lux or above), but when used in a darker place, theilluminance is too low to enable the viewer to perceive the display.

[0500] A relation of the adapted luminance versus the sample luminancewhen the reflectance is 50% is shown as a straight line 603 in FIG. 30.As can be understood from the straight line 603, when the reflectivedisplay is shown at the reflectance of 50% or above as with normal whitepaper, the perceived brightness exceeds 30 brils under the highilluminance circumstances of 1800 lux or above (for example, a brightinterior near the window, or under direct sunlight) Under thesecircumstances, the viewer feels the white paper is too bright. Thus, itis not appropriate to use the display surface having the reflectance of50% or above under the high illuminance circumstance from the standpointof the visibility, and it can be understood that preferable reflectanceof the display surface (luminance surface) for the reflection displayused under these circumstances is 30% or so.

[0501] On the other hand, in the reflection display at the reflectanceof 30% and the reflection display at the reflectance of 10% respectivelyshown as the straight lines 601 and 602, the illuminance which can givethe perceived brightness of 10 brils is about 450 lux and 3000 lux,respectively. In other words, when the reflectance decreases to onethird, the illuminance 6.7 times brighter is necessary. This means that,if the illuminance is increased because the reflectance of the liquidcrystal display decreases, the eyes of the human adapt to a brightreflective object other than the liquid crystal display, and theillumination must be raised more than the reciprocal of a changing ratioof the reflectance.

[0502] Further, as can be understood from FIG. 30, there is a problemthat the viewer feels that the display on a display body (for example, atypical display of the illuminance type) having predetermined luminanceis very dark when the surroundings are bright.

[0503] However, the liquid crystal display of the transflective type ofthe present invention uses for display a sum of a predeterminedluminance determined by the back light and the transmittance in thetransmission display section, and an luminance (sample luminance)determined by predetermined reflectance in the reflection displaysection. In other words, in the liquid crystal display of thetransflective type of the present invention, the display at the displayluminance indicated by a curve 604 in FIG. 30 can be realized, forexample. As indicated by the curve 604, in the liquid crystal display ofthe transflective type of the present invention, the visibility issecured by the reflection display when the illuminance is high, whilethe visibility is secured by the transmission display using the lightingdevice (back light) as the back light means when the illumination islow.

[0504] Next, the perceived brightness was checked when changing theilluminance using the surface luminance of the above liquid crystaldisplay of the transflective type, the result of which is set forth inFIG. 31. Also, relations of the illuminance versus the perceivedbrightness in the liquid crystal displays of the transmission type andreflectance type are respectively set forth in FIG. 31 for comparison.Here, the conditions for computing the perceived brightness are: thereflectance is 30% when the entire display area is used for thereflection display of color; the transmittance is 7.5% when the entiredisplay area is used for the transmission display; the luminance of theback light is 2000 cd/m²; the illuminance of the surface to which theviewer is adapted is equal to the illuminance of the display surface ofthe liquid crystal display of color; and the reflectance of the adaptedobject surface is assumed to be 20% based on the brightness of N5 onMunsell color standard.

[0505] In FIG. 31, a value of the perceived brightness when theilluminance is varied depends on a ratio (Sr) of the reflection displaysection in the displayable area on the liquid crystal display of thetransflective type. curve 611 shows a relation of the illuminance versusperceived brightness when the normal liquid crystal display of thetransmission type shows the transmission display alone, that is whenSr=0. The luminance on the display surface of the liquid crystal displayof the transmission type is 150 cd/m², and when the illuminance is 6000lux or above, the perceived brightness is 10 brils or below. Thus, tosecure the perceived brightness of 10 brils or above by changing a partof the transmission display section to the reflection display section,as is indicated by the curve 612, Sr=0.1, that is {fraction (1/10)} ofthe displayable area should be used as the reflection display section.

[0506] A curve 613 shows a relation of the illuminance versus theperceived brightness of the liquid crystal display of the reflectiontype which shows the reflection display alone, that is, Sr=1. Thereflectance of the display surface on the liquid crystal display of thereflection type is 30% compared with a perfect reflecting diffusersurface, and when the illuminance is 450 lux or below, the perceivedbrightness is 10 brils or below. Thus, to secure the perceivedbrightness of 10 brils or above by changing a part of the reflectiondisplay section to the transmission display section, as is indicated bythe curve 614, Sr=0.9, that is, {fraction (1/10)} of the displayablearea should be used as the transmission display section.

[0507] Also, as can be understood from FIG. 31, when Sr is in a rangebetween 0.1 and 0.9, satisfactory display with the perceived brightnessof 10 brils or above and less than 30 brils can be shown. When Sr is setto 0.30 (curve 615) or 0.50 (curve 616), satisfactory light display withthe perceived brightness of 20 brils or above and less than 30 brils canbe shown.

[0508] Also, surface reflection occurs on the surface of liquid crystaldisplays. The surface reflection interferes with the display moremarkedly as the illuminance of the surrounding rises. In FIG. 31, arelation of the perceived brightness and illuminance caused by thesurface reflection is shown (curve 617). Though the surface reflectionis affected considerably by the finish of the surface, the curve 617shows the relation of the perceived brightness form the surfacerefection versus illuminance in case that the surface reflection causedat the interface between air and a medium having a refractive index of1.5 has the same diffusing abilities as a perfect diffuse surface (thatis, when the reflectance by surface reflection is 4%). Thus, when thesurface reflectance is taken into consideration, in order to obtainsatisfactory display, it is preferable if an area of the reflectiondisplay section accounts for 30% or above (that is, Sr>0.3) of a totalof areas of the reflection display section and transmission displaysection.

[0509] According to the above analysis, it is understood that,satisfactory color display can be shown both in the reflection displaysection and transmission display section of the liquid crystal of thepresent embodiment when the area of reflection display section accountsfor 30% or above and 90% or below of a total of the areas of thereflection display section and transmission display section.

[0510] A ratio of each display section for showing satisfactory displaycan be analyzed in the above manner even when at least one of thereflection display and transmission display is not used for the colordisplay. However, in any case, the satisfactory display can be realizedwhen a ratio of the area of the reflection display section in a total ofareas of the reflection display section and transmission display sectionis in the above specified range. The liquid crystal displays of thetransmission-main transflective type and the reflection-maintransflective type of Example 7 are assembled using a preferable ratioin the above specified range.

Embodiment 9

[0511] In the present embodiment, an active matrix liquid crystaldisplay adopting the liquid crystal display method described inEmbodiments 1 and 2, to be more specific, a liquid crystal display forshowing the color display using the TFT element substrate, will beexplained by way of examples for purposes of explanation only, withoutany intention as a definition of the limits of the invention.

[0512] A procedure for assembling the active matrix liquid crystaldisplay of the present embodiment is composed of a process of producingthe TFT element substrate; a process of producing the color filtersubstrate; a process of producing a liquid crystal cell for fillingusing the TFT element substrate and color filter substrate; and aprocess of assembling the liquid crystal display by filling the liquidcrystal into the liquid crystal cell for filling obtained in thepreceding process.

[0513] Thus, the manufacturing method of the active matrix liquidcrystal display of each example below in the present embodiment will beexplained from the process of producing the TFT element substrate, tobegin with.

[0514] As shown in FIGS. 23(a) through 25, the TFT element substrate iscomposed of a light transmitting substrate 29 on which is formed a TFTelement 21 for each pixel by the following steps.

[0515] Here, a glass substrate made of a substance having no alkalicontents, such as non-alkali glass, is used as the substrate 29 on whichthe TFT elements 21 are formed. In the first place, a film of tantalumis sputtered on the substrate 29, which will be made into the line 23 asthe gate line and the storage capacitor line 27 by patterning. The line23 and storage capacitor line 27 are patterned in such a manner as tohave gradual step in each (line 23 and storage capacitor line 27), sothat they can be covered satisfactorily with the line 24 formed thereonin the later stage to prevent line disconnection.

[0516] Further, a layer of tantalum oxide (Ta₂O₅) is formed over theline 23 and storage capacitor line 27 by the anodic oxidation process,over which a film of silicon nitride which will serve as a gateinsulation film is formed. Then, a layer of hydrogenated amorphoussilicon as an intrinsic semiconductor layer (i layer) which will be madeinto a switching region of the TFT element 21 and a layer of siliconnitride as an etching stopper layer are formed in this order by the CVD(Chemical Vapor Deposition) method using monosilane gas and sputtering(silicon nitride), respectively. Then, the top layer (silicon nitridelayer) is patterned as the etching stopper layer, after which an n⁺layer, which will be made into the source terminal 28 and drain terminal22 of the TFT element 21, is formed by the CVD method using a monosilanegas mixed with a phosphine gas. Subsequently, the n⁺ layer and i layerare patterned, and further, the gate insulation film is patterned. Here,silicon nitride on the connection terminal portion on the line 23 (gateline) outside the display region is removed.

[0517] Next, a film of ITO, which will be made into the transparentpixel electrode 20, is sputtered in such a manner as to touch the sourceterminal 28 and drain terminal 22, and a film of tantalum, which will bemade into the line 24 as the source line, is sputtered. The tantalumfilm is patterned into the line 24, and the ITO film formed beneath thetantalum film is patterned into the transparent pixel electrode 20. Aspreviously mentioned, the transparent pixel electrode 20 is connected tothe source terminal 28 and drain terminal 22, and it also forms ohmiccontact between these terminals (source terminal 28 and drain terminal22) and the lines 23 and 24.

[0518] Next, the organic insulation film 25 having the protrusions anddepressions on the surface is formed on the TFT element 21 as theinsulation film of the reflection display section. Then, a film ofaluminum, which will be made into the driving electrode 19 of thereflection display section 9, is sputtered in such a manner as to touchthe transparent pixel electrode 20 at a contact hole formed through theorganic insulation film 25 to serve as the transmission display opening.Subsequently, the aluminum film is patterned by means of the dryetching, whereby the driving electrode 19 serving as the reflectiveelectrode on which are provided the same protrusions and depressions asthose on the surface of the organic insulation film 25 is formed.

[0519] In each of the above patterning steps, each component is formedinto a necessary shape based on a design, by means of thephotolithographic technique. In the photolithographic steps, the stepsof coating and drying photosensitive resin (resist), irradiating thepattern, developing, baking and curing the resist, dry etching, wetetching, removing the resist, etc. are combined.

[0520] The protrusions and depressions are formed in the reflectiondisplay section 9 by applying an insulation photopolymeric resinmaterial thereon and subjecting the same successively to the patternirradiating step, developing step, and curing step. In other words, adot pattern is formed in the developing step, and a smoothing layer isformed on the dot pattern out of the same material. Here, the organicinsulation layer 25 is not formed in the transmission display section10.

[0521] The TFT element 21 is provided to each pixel in the TFT elementsubstrate produced in the above steps, and each pixel is composed of therefection display section 9 and transmission display section 10. Here,two types of TFT element substrate are produced: the TFT elementsubstrate of FIG. 23(a) and the TFT element substrate of FIG. 28, and aratio of the transmission display section 10 and reflection displaysection 9 in each type is set as described in Embodiment 7.

[0522] Next, the procedure of producing the color filter substrate willbe explained. This procedure is composed of a step of producing the RGBcolor layers (color filters) on the substrate, a step of forming asmoothing layer on the color filters, and a step of forming a counterelectrode to the transparent pixel electrode 20 formed on the TFTelement substrate driven by the TFT element 21.

[0523] In the present embodiment, as shown in FIG. 26(b) or FIG. 29(b),the color filter 61R for red (R), color filter 61G for green (G), andcolor filter 61B for blue (B) are formed on the glass substrate 62 instripes. Then, a smoothing layer 501 is formed on the glass substrate 62on the surface where the color filters 61R, 61G, and 61B are formed tocover the same, and the counter electrode 502 is formed on the smoothinglayer 501, whereby the color filter substrate is formed.

[0524] During the step of forming the color filter substrate, the colorfilters 61R, 61G, and 61B are formed by using photolithography topattern a resin material prepared by dispersing the pigment inphotosensitive resin. The method of producing the color filters 61R,61G, and 61B is not limited to the above method using the dispersedpigment, and for example, the electro-deposition method, film transfermethod, and dying process can be adopted as well.

[0525] The smoothing layer 501 is formed by applying acrylate resinhaving high light transmittance on the glass substrate 62 on the surfacewhere the color filters 61R, 61G, and 61B are formed, and curing thesame by heat. The counter electrode 502 formed on the smoothing layer501 is a counter electrode opposing the pixel electrode 18 driven by theTFT element 21, and is formed as a transparent electrode by sputteringlayers of ITO with masking and shaping the resulting deposit of the ITOlayers into a planar shape.

[0526] In the present embodiment, two types of color filter substratesare formed: the color filter substrate having high chroma for thetransmission display, and the color filter substrate having highbrightness for the reflection display. The former is patterned as shownin FIGS. 26(a) and 26(b), and the latter is patterned as shown in FIGS.29(a) and 29(b).

[0527] Next, the step of producing the liquid crystal cell for fillingby placing the TFT element substrate and color filter substrate tooppose each other to assemble the liquid crystal layer will beexplained.

[0528] In this step, alignment films are formed on the TFT elementsubstrate and color filter substrate on their respective opposingsurfaces (the surface where the TFT element 21 is formed on the TFTelement substrate and the surface where the color filters 61R, 61G, and61B are formed on the color filter substrate) by applying a solublepolyimide solution in the liquid crystal display area by the offsetprinting method, and subjecting the same to the drying and baking steps.Further, the alignment treatment, which determines the alignmentdirection of the liquid crystal, is applied to these alignment films bymeans of rubbing. Whether the parallel aligning alignment films orperpendicular aligning films are used depends on each example.

[0529] Subsequently, spherical spacers of the uniform particle size arescattered on one of the TFT element substrate and color filter substratetreated in the above manner, and a sealing agent for sealing the liquidcrystal layer in a space between the TFT element substrate and colorfilter substrate and fixing these substrates is printed to the othersubstrate. Meanwhile, conductive paste is provided to let the currentflow from the TFT element substrate side to the counter electrode 502 onthe color filter substrate.

[0530] Then, the TFT element substrate and color filter substrate areplaced to oppose each other with surface provided with the TFT element21 and the surface provided with the color filters 61R, 61G, and 61Binside, and after the positions of these substrates are aligned withrespect to each other, the sealing agent and conductive paste are curedunder applied pressure.

[0531] By the above procedure and steps, the mother glass substrate 21containing a plurality of the liquid crystal cells for filling isproduced, and the filling cells are produced by cutting the mother glasssubstrate 21.

[0532] Later, the liquid crystal composition is introduced into theliquid crystal cell by means of vacuum injection, and photopolymericresin is applied at the inlet of the liquid crystal and cured throughpolymerization upon irradiation of UV rays, so that the liquid crystallayer filled therein will not be exposed to air, whereby the liquidcrystal cell is produced.

[0533] Then, a short-ring portion, provided at the end portion of theTFT element substrate to short-circuit the line terminals to prevent theelectrostatic breakdown of the TFT element 21, is removed to connect theTFT element 21 to an external circuit for driving the TFT element 21.Further, the back light serving as the light source for the transmissiondisplay is provided, whereby the active matrix liquid crystal display ofthe present embodiment is assembled.

EXAMPLE 14

[0534] The active matrix liquid crystal display of the present exampleis a liquid crystal display of the transmission-main transflective typeadopting the GH method, which uses for display the same GH method asthat used in the liquid crystal display of Example 1 in Embodiment 1.

[0535] The liquid crystal composition used in the present example isprepared in the same manner as Example 1 in Embodiment 1. In otherwords, the liquid crystal composition using the dichroic dye (dichroicdye 12) used in Example 1 is used herein too. Also, in the presentexample, vertical aligning alignment films which align the liquidcrystal perpendicular to the display surface are used, and the alignmenttreatment is applied to these alignment films in such a manner as toobtain uniform vertical alignment. In the present example, neither thephase difference compensation plates nor polarization plates arelaminated to the liquid crystal cell, because the GH method using thedichroic dye as the liquid crystal composition is adopted.

[0536] In the present example, since the transmission display is mainlyused, the color filters 61R, 61G, and 61B are designed to have chroma ashigh as that in the conventional transmission display method, and thecolor filter substrate is placed as shown in FIGS. 26(a) and 26(b). TheTFT element substrate laminated to the color filter substrate has alarge transmission display opening 19 a and a wide transmission displaysection 10, as shown in FIG. 23(a).

[0537] As shown in FIGS. 26(a) and 26(b), in the liquid crystal displayof the present example, only a specific portion of the driving electrode19 of the reflection display section 9 is covered with the color filters61R, 61G, and 61B covering the transmission display opening 19 a whichwill serve as the transmission display section 10 (a portion opposingthe color filters 61R, 61G, and 61B in the extending direction thereof).The driving electrode 19 also has a display portion which has no colorfilter and thereby transmits white light.

[0538] A display signal was inputted into the liquid crystal displayassembled in the above manner, and the liquid crystal display wasobserved visually. Then, it turned out that, with the liquid crystaldisplay of the present example, the back light has to be turned ON.However, with the back light kept turned ON, the brightness and contrastratio are both satisfactory, and satisfactory display is always shownthereon. Further, the display content can be observed visibly underdirect light, and there occurs no wash-out.

[0539] In other words, in the present example, it has become possible toprovide a high-resolution color liquid crystal display without causingwash-out nor parallax, which can attain high brightness by using theback light when the ambient light is weak, as does the conventionalliquid crystal display, while enabling the user to observe the displaycontent even when the ambient light is strong by changing the brightnessof the reflection display section 9 in proportion to the ambient light.In addition, in the present example, very satisfactory reflectiondisplay having no parallax (double image) can be realized.

EXAMPLE 15

[0540] The active matrix liquid crystal display of the present exampleis a liquid crystal display of the reflection-main transflective typeadopting the GH method, which uses for display the same GH method asthat used in the liquid crystal display of Example 1 in Embodiment 1.

[0541] Like in Example 14, the liquid crystal composition used in thepresent example is prepared in the same manner as Example 1 inEmbodiment 1. In other words, the liquid crystal composition containingthe dichroic dye (dichroic dye 12) used in Example 1 is used herein too.Also, in the present example, vertical aligning alignment films whichalign the liquid crystal perpendicular to the display surface are used,and the alignment treatment is applied to these alignment films by meansof rubbing in such a manner as to obtain uniform vertical alignment. Inthe present example, neither the phase difference compensation platesnor polarization plates are laminated to the liquid crystal cell,because the GH method using the dichroic dye as the liquid crystalcomposition is adopted.

[0542] In the present example, since the reflection display is mainlyused, the color filters 61R, 61G, and 61B are designed to havebrightness higher than that in the conventional liquid crystal displayof the transmission type, and the color filter substrate is placed asshown in FIGS. 29(a) and 29(b). The TFT element substrate laminated tothe color filter substrate has a small transmission display opening 19 aand a wide reflection display section 9, as shown in FIG. 28.

[0543] A display signal was inputted into the liquid crystal displayassembled in the above manner, and the liquid crystal display wasobserved visually. Then, it turned out that the present liquid crystaldisplay can show the reflection display without turning ON the backlight when used during the day time under indoor lighting or surroundingexterior light. In the present example, very satisfactory reflectiondisplay having no parallax (double image) can be realized. Also, thedisplay content can be visually confirmed by turning ON the back lightwhen the ambient light is too weak for the user to observe the displayusing reflected light alone.

[0544] To be more specific, in the present example, the color filters61R, 61G, and 61B and the color filter substrate used are designed forthe reflection transmission as previously mentioned, and thus the colordisplay can be shown by the reflected light alone. Consequently, thepresent liquid crystal display can be used with the reflection displayalone while keeping the back light turned OFF for the use in indoorlighting or outdoor during the day time. In addition, the visibility canbe secured even when the lighting is too weak by turning ON the backlight, as needed.

[0545] Unlike the conventional liquid crystal display of thetransmission type, the back light does not have to be kept turned ON inthe liquid crystal display of the present embodiment. Consequently, thepresent liquid crystal display can save the power consumption whilecausing no wash-out in the reflection display section 9; moreover, itcan show the transmission display using the back light, as needed.

EXAMPLE 16

[0546] The active matrix liquid crystal display of the present exampleis a liquid crystal display of the transmission-main transflective typeusing the polarization converting function of the liquid crystal layerfor the display, which uses for display the same polarization platemethod as used in the liquid crystal display of Example 5 in Embodiment2.

[0547] The liquid crystal composition used in the present example isprepared in the same manner as Example 5 in Embodiment 2. Herein, thephase difference compensation plates (phase difference compensationplates 16 and 17) and polarization plates (polarization plates 14 and15) are laminated to the liquid crystal cell (TFT liquid crystal panel)in which is sealed the liquid crystal. Further, in the present example,the alignment treatment is applied to the parallel aligning alignmentfilms by means of rubbing in such a manner as to form the crossedrubbing angle of 250°.

[0548] Like in Example 14, in the present example, since thetransmission display is mainly used, the color filters 61R, 61G, and 61Bare designed to have the same transmission colors as those in theconventional transmission display method, and the color filter substrateis placed as shown in FIGS. 26(a) and 26(b). The TFT element substratelaminated to the color filter substrate has a large transmission displayopening 19 a and a wide transmission display section 10 as shown in FIG.23(a).

[0549] As shown in FIGS. 26(a) and 26(b), in the liquid crystal displayof the present example, only a specific portion of the driving electrode19 in the reflection display section 9 is covered with the color filters61R, 61G, and 61B covering the transmission display opening 19 a whichwill serve as the transmission display section 10 (a portion opposingthe color filters 61R, 61G, and 61B in the extending direction thereof).The reflection display section 9 also has a display portion which has nocolor filter and thereby reflects white light.

[0550] A display signal was inputted into the liquid crystal displayassembled in the above manner, and the liquid crystal display wasobserved visually. Then, it turned out that, with the liquid crystaldisplay of the present example, the back light has to be kept turned ON.However, with the back light kept turned ON, the brightness and contrastratio are both satisfactory, and satisfactory display is always shownthereon. Further, the display content can be observed visibly underdirect sunlight, and there occurs no wash-out.

[0551] In other words, in the present example, a liquid crystal displayattaining high brightness by using the back light when the ambient lightis weak, as does the conventional liquid crystal display of thetransmission type is provided, and on the other hand, even when theambient light is strong, the display content can be confirmed visuallyby changing the brightness of the reflection display section 9 inproportion to the ambient light, thereby eliminating the wash-out causedin the conventional display of the illuminance type or liquid crystaldisplay of the transmission type. Further, in the present example, verysatisfactory reflection display having no parallax (double image) can berealized.

EXAMPLE 17

[0552] The active matrix liquid crystal display of the present exampleis a liquid crystal display of the reflection-main transflective typeusing the polarization converting function of the liquid crystal layerfor the display, which uses for display the same polarization platemethod as that used in the liquid crystal display of Example 5 inEmbodiment 2.

[0553] Like in Example 16, the liquid crystal composition used in thepresent example is prepared in the same manner as Example 5 inEmbodiment 2. Herein, the phase difference compensation plates (phasedifference compensation plates 16 and 17) and polarization plates(polarization plates 14 and 15) are laminated to the liquid crystal cell(TFT liquid crystal panel) in which is sealed the liquid crystal.Further, in the present example, the alignment treatment is applied tothe parallel aligning alignment films by means of rubbing in such amanner as to form the crossed rubbing angle of 250°.

[0554] Also, like in Example 15, since the reflection display is mainlyused, the color filters 61R, 61G, and 61B are designed to havebrightness higher than that in the conventional liquid crystal displayof the transmission type, and the color filter substrate is placed asshown in FIGS. 29(a) and 29(b). The TFT element substrate laminated tothe color filter substrate has a small transmission display opening 19 aand a wide reflection display section 9 as shown in FIG. 28.

[0555] A display signal was inputted into the liquid crystal displayassembled in the above manner, and the liquid crystal display wasobserved visually. Then, it turned out that the present liquid crystaldisplay can show the reflection display without turning ON the backlight when used during the day time under indoor lighting or surroundingexterior light. In the present example, very satisfactory reflectiondisplay having no parallax (double image) can be realized. Also, thedisplay content can be visually confirmed by turning ON the back lightwhen the ambient light is too weak for the user to observe the displayusing reflected light alone.

[0556] To be more specific, in the present example, the color filters61R, 61G, and 61B and color filter substrate used are designed for thereflection display as previously mentioned, and thus the color displaycan be shown by the reflected light alone. Consequently, the presentliquid crystal display can be used with the reflection display alonewhile keeping the back light turned OFF when used either in indoorlighting or outdoors during the day time. In addition, even when thelighting is too weak, the visibility can be secured by turning ON theback light, as needed.

[0557] Unlike the conventional liquid crystal display of thetransmission type, the back light does not have to be kept turned ON inthe liquid crystal display of the present embodiment. Consequently, thepresent liquid crystal display can save the power consumption whilecausing no wash-out in the reflection display section 9; moreover, itcan show the transmission display using the back light, as needed.

[0558] As has been discussed by way of Examples 14 through 17, accordingto the present embodiment, a high-resolution active matrix liquidcrystal display adopting the liquid crystal display method of Embodiment1 or 2 can be realized.

[0559] In Examples 14 through 17, each liquid crystal display isassembled to have different thicknesses of the liquid crystal layer inthe reflection display section 9 and transmission display section 10 byproviding the organic insulation film 25 (equivalent to insulation film11) on the active matrix substrate (TFT element substrate). However, itshould be appreciated that the same effect can be attained when anyother liquid crystal display principle of the present invention isadopted.

Embodiment 10

[0560] The present embodiment will explain how the luminance of the backlight used in the liquid crystal display of the present invention ischanged.

[0561] The luminance of the back light is changed mainly for the threefollowing reasons.

[0562] A first purpose is to secure the visibility. As has beendiscussed in Embodiment 8, the perceived brightness perceived by a humanis determined by the adapted luminance and the luminance of the displaysurface. Thus, to realize satisfactory display with satisfactoryvisibility, it is effective to change the luminance of the back light tothe perceived brightness of human eyes in response to the adaptedluminance. As described in Embodiment 8, it is preferable to change theluminance of the display surface by controlling the luminance of theback light in response to the adapted luminance, so that the perceivedbrightness is in a range from 10 brils inclusive to 30 brils exclusive.In short, the back light also serves as display surface luminancechanging means. Consequently, the visibility can be improved when thetransmission display is mainly responsible for the display. Here, avalue of the perceived brightness specified in Embodiment 8 is set onthe assumption that the luminance of the display surface is proportionalto the adapted luminance to which the viewer has adapted. Thus,satisfactory display can be obtained only by changing the luminance ofthe back light in accordance with the perceived brightness.

[0563] A second purpose is to save the power consumption. There arecases where the visibility is not affected much whether the back lightis turned ON or OFF. An example of such a case would be when a liquidcrystal display of the transflective type is used where the ambientlight lighting the liquid crystal display has sufficiently highilluminance, so that the luminance of the display surface is maintainedmainly by the reflection display section. In this case, the luminance ofthe display surface may not be affected even if the luminance of thetransmission display is high, and in such a case, it is preferable toturn OFF the back light to save the power consumption.

[0564] A third purpose is to furnish more than one function to theliquid crystal display by enabling the user to switch the color displayto the monochrome display and vice versa by turning ON/OFF the backlight, in cases where the color display is shown by either thereflection display or transmission display alone.

[0565] For example, when the reflection display section is not providedwith the color filters, and shows the monochrome display alone, and thetransmission display section alone is provided with the color filters toshow the color display, the resolution of the reflection display can beset higher than in the transmission display section which displays onemonochrome unit by a plurality of pixels using color filters.Consequently, the reflection display is high-resolution monochromedisplay, while the transmission display is color display with moderateresolution. Conversely, the color filters may be used for the reflectiondisplay alone. In this case, more than one function can be provided tothe liquid crystal display. Consequently, it has become possible tochange the display content significantly in response to the ON/OFF stateby switching the color display to the monochrome display and vice versaor changing the illuminating colors by turning ON/OFF the back light.

[0566] As has been discussed above, the luminance of the back light canbe controlled by an adequate signal in response to the intended use oruse conditions. When the luminance of the back light is changed inresponse to the aforementioned adapted luminance, to improve thevisibility, the luminance of the back light is controlled in response tothe visual environment, such as the illuminance of the light incident onthe display surface, and the kinds of the display adopted by the liquidcrystal display.

[0567] When the luminance of the back light is controlled in response tothe illuminance, it is preferable to control the ON/OFF state of theback light in the following manner. That is, the back light is turnedOFF when the illuminance is high, whereas the back light is turned ON ina moderate state when the illuminance is low so as to avoid excessivebrightness, and the back light is turned ON in a strong state when theilluminance is neither too high nor too low.

[0568] In this case, if the ON/OFF state of the back light or theluminance thereof are controlled by a signal from external devices or atimer connected to the liquid crystal cell or liquid crystal display,unnecessary power consumption can be saved.

[0569] Further, in controlling the luminance of the back light, if heback light is only turned ON when the user manipulates the apparatusincluding the liquid crystal display, or for a fixed period thereafter,the overall power consumption of the apparatus can be saved, and theuser can be provided with display he feels to be satisfactory. Theluminance of the back light may also be controlled by any otherapplicable signal besides the illuminance of the light incident on thedisplay surface.

[0570] To achieve the above objects, it is very effective to allow theuser to control the ON/OFF state of the back light or the luminancethereof, or the director configuration of the liquid crystal in thereflection display section and transmission display section by inputtinga signal through a touch panel (pressed coordinate detecting type inputmeans) layered on the display surface of the liquid crystal cell, or bycontrolling the luminance of the back light in association with someother signal giving a warning to the user. In this manner, a liquidcrystal display with visibility and consuming less power can be providedby controlling the luminance of the display surface from the outside ofthe liquid crystal cell.

Embodiment 11

[0571] Explained in the present embodiment is a liquid crystal displayof the present invention, provided with a touch panel (pressedcoordination detecting type input means) as information input means, andused in a portable device, which is the field in which the liquidcrystal display of the present invention is chiefly used. Hereinafter,like components are labeled with like reference numerals with respect toEmbodiments 1 through 10, and, for ease of explanation, the descriptionof these components is not repeated here.

[0572] In the present embodiment, a touch panel is attached to theliquid crystal display of Example 17 in Embodiment 9, whereby a liquidcrystal display of the transmission type incorporating an input deviceis assembled, the arrangement of which is illustrated in FIG. 32. Thebasic arrangement of the liquid crystal display of the presentembodiment, that is, the liquid crystal cell and back light 13, isidentical with the arrangement of Example 17 in Embodiment 9 and Example5 in Embodiment 2 except for the touch panel 71, and, for ease ofexplanation, the description of these components is not repeated here.

[0573] The touch panel 71 includes a flexible substrate 73 on which isformed a transparent electrode layer 72 and a supporting substrate 75 onwhich is formed a transparent electrode layer 74. The flexible substrate73 and supporting substrate 75 are placed to oppose each other withtheir respective transparent electrode layers 72 and 74 inside, withspacers (not shown) maintaining a predetermined distance therebetween sothat, when they are supplied with an electrical current, the transparentelectrode layers 72 and 74 do not touch each other. According to thisarrangement, the transparent electrode layer 72 formed on the flexiblesubstrate 73 and the transparent electrode layer 74 formed on thesupporting substrate 75 keep a space from each other under the normalstate, and are allowed to touch each other at a position only when sucha position on the flexible substrate 73 is specified (pressed) by afinger or a stylus. Accordingly, the touch panel 71 functions as aninput device by detecting a position (coordinate position) where thetransparent electrodes 72 and 74 touch each other by a pressing forceapplied on the flexible substrate 73.

[0574] The touch panel 71 is provided between the phase differencecompensation plate 16 and substrate 4 of the liquid crystal cell bylaminating the phase difference compensation plate 16 and polarizationplate 14 on the flexible substrate 73, so that it forms an integral unittogether with the phase difference compensation plate 16 andpolarization plate 14. In the present embodiment, to attain the effectof the polarization plate of Example 17 by the polarization plate 14laminated to the touch panel 71, both the flexible substrate 73 andsupporting substrate 75 forming the touch panel 71 are made of amaterial having no birefringence.

[0575] In the present embodiment, a space is secured between thesupporting substrate 75 of the touch panel 71 and the substrate 4 of theliquid crystal cell, so that the pressure applied on the touch panel 71is not transferred to the liquid crystal cell without using a pressuredamping member, whereby the touch panel 71 and substrate 4 of the liquidcrystal cell can attain a pressure transfer preventing effect.

[0576] In the liquid crystal display incorporating the input deviceassembled in the above manner, the back light 13 can be turned OFF whenthe user does not observe the display and turned ON upon input ofinformation into the touch panel 71 by changing the luminance of theback light 13 in response to signals from the touch panel. Consequently,the liquid crystal display of the present embodiment can showsatisfactory display while saving the power consumption. In addition,according to the present embodiment, visibility can be improved byproviding the polarization plate 14, touch panel 71, and liquid crystalcell in this order, because the polarization plate 14 also absorbsunwanted reflected light from the touch panel 71, thus reducing suchunwanted reflected light.

[0577] As has been explained, a liquid crystal display of the presentinvention is arranged in such a manner as to comprise:

[0578] a liquid crystal display element having a pair of substrates, towhich alignment members (alignment means), such as alignment films, areprovided to their respective opposing surfaces, and a liquid crystallayer sandwiched by the pair of substrates;

[0579] alignment mechanism for providing at least two different directorconfigurations simultaneously on different arbitrary regions used fordisplay in the liquid crystal layer; and

[0580] a reflecting member (reflecting means), such as a reflection filmor a reflective electrode, provided to at least one of the differentarbitrary regions showing different director configurations,

[0581] wherein the different arbitrary regions showing differentdirector configurations are used for a reflection display section forshowing reflection display and a transmission display section forshowing transmission display, respectively.

[0582] According to the above arrangement, the director configuration ofthe liquid crystal can take different director configurationssimultaneously. Thus, for example, an amplitude of modulation in anopti-physical quantity, such as an amount of absorbed light (absorbance)when a light absorber like a dichroic dye is used for the display, and aphase difference when optical anisotropy is used for the display, can bechanged separately in each region. Thus, according to the abovearrangement, it is possible to obtain transmittance or reflectance basedon an amplitude of modulation in an opti-physical quantity in responseto the director configuration of the liquid crystal layer, therebymaking it possible to set the transmission display section andtransmission display section independently. Hence, according to theabove arrangement, a high contrast ratio can be attained without causingparallax and the visibility can be improved when the surroundings aredark, while satisfactory visibility can be attained even when theambient light is strong. Consequently, according to the abovearrangement, it has become possible to provide a liquid crystal displayof the transflective type, having excellent visibility, and capable ofshowing high-resolution display and using both the reflected light andtransmitted light for the display.

[0583] One alignment mechanism which may be suitably used is displaycontent overwriting means for overwriting a display content with anevolution of time. In this case, the display content overwriting meansand the alignment mechanism are realized by a single means, so that theabove liquid crystal display can be obtained without adding anyadditional members. It should be appreciated that, however, electricalliquid crystal alignment control means currently used extensively foroverwriting the display content with an evolution of time, namely, anyapplicable means used for voltage application, such as electrodes, canbe used as the display content overwriting means for realizing more thanone state of director configuration of the liquid crystal. In this case,a plurality of regions having different director configurations can beprovided in the liquid crystal layer by using different electrodes inthe transmission display section and reflection display section, orchanging the voltage itself in the transmission display section andreflection display section.

[0584] Also, in case that an amplitude of modulation in an opti-physicalquantity, such as an amount of absorbed light and a phase differencecaused by the optical anisotropy, is set independently in the reflectiondisplay section and transmission display section, even if the alignmentdirection of the liquid crystal obtained by the voltage application issubstantially uniform across the region used for the display in theliquid crystal layer, in regions having different thicknesses of theliquid crystal layer, there can be offered the same effect as the oneattained in the case where the alignment direction of the liquid crystallayer is changed. In particular, in the GH method (which uses a lightabsorber like a dichroic dye and makes use of light absorption) or thepolarization plate method which makes use of birefringence orpolarization rotation phenomenon), the phenomena, (such as lightabsorption or birefringence) occurring in the liquid crystal layer, arethe phenomena that take place in association with the light propagation,and thus a relation is established between the distance of the lightpropagation in the liquid crystal layer and the degree of eachphenomenon. Further, the display light passes through the liquid crystallayer twice in the reflection display section and only once in thetransmission display section. Thus, when the director configuration ofthe liquid crystal is substantially the same in the reflection displaysection and transmission display section, neither sufficient brightnessnor contrast ratio can be obtained if the thickness of the liquidcrystal layer is the same in the reflection display section andtransmission display section, thereby making it impossible to eliminatethe above problems.

[0585] Therefore, a liquid crystal display of the present invention maybe arranged in such a manner as to comprise a liquid crystal displayelement having a pair of substrates, to which alignment means areprovided to their respective opposing surfaces, and a liquid crystallayer sandwiched by the pair of substrates, wherein:

[0586] a region used for display in the liquid crystal layer is composedof regions having at least two different thicknesses of the liquidcrystal layer;

[0587] the regions having at least two different thicknesses are usedfor a reflection display section and a transmission display section,respectively;

[0588] reflecting means is provided at least to the reflection displaysection; and

[0589] the thickness of the liquid crystal layer is thinner in thereflection display section than in the transmission display section.

[0590] According to the above arrangement, it is possible to obtain thetransmittance or reflectance based on an amplitude of modulation in anopti-physical quantity in the regions having different thicknesses ofthe liquid crystal layer, thereby making it possible to set thetransmission display section and transmission display sectionindependently. Hence, according to the above arrangement, a highcontrast ratio can be attained without causing parallax and thevisibility can be improved when the surroundings are dark, whilesatisfactory visibility can be attained even when the ambient light isstrong. Consequently, according to the above arrangement, it has becomepossible to provide a liquid crystal display of the transflective type,having excellent visibility and capable of showing high-resolutiondisplay and using both the reflected light and transmitted light for thedisplay.

[0591] The above-arranged liquid crystal display of the presentinvention may be arranged in such a manner that, in order to provide atleast two different director configurations simultaneously on differentarbitrary regions used for display in the liquid crystal layer, analignment means is provided in a region of the surface at least one ofthe substrates touching a region of the liquid crystal layer used fordisplay, so as to impart at least two different director directions toan director configuration of the liquid crystal layer at an interfacetouching the region in which the alignment mechanism is provided.

[0592] Besides the above display content overwriting means, an alignmentfilm provided on the substrate at the interface touching the liquidcrystal, to which the alignment treatment is applied in such a manner asto impart at least two different directions of director to the directorconfiguration of the liquid crystal layer at the interface touching tothe same, can be used as the means for allowing the directorconfiguration of the liquid crystal to take different directorconfigurations simultaneously. By providing the alignment means in aregion of the surface of the substrate touching the region of the liquidcrystal layer used for display so as to impart at least two differentdirector directions to the director configuration of the liquid crystallayer at the interface touching the region in which the alignment isprovided, the liquid crystal layer can take at least two differentdirector configurations simultaneously upon the voltage application atdifferent arbitrary regions used for the display in the liquid crystallayer, and as a consequence, the reflection display and transmissiondisplay can be shown respectively in these regions having differentdirector configurations in the liquid crystal layer.

[0593] In this case, the director configuration of the liquid crystalthat determines the optical characteristics and a change of thealignment upon the voltage application can both be changed by modifyingan angle of the director configuration of the liquid crystal layer withrespect to the substrate or an orientation angle, thereby allowing eachof the reflection display section and transmission display section toshow adequate display thereon.

[0594] It is preferable that the liquid crystal display of presentinvention is arranged in such a manner that at least one of the pair ofsubstrates includes an insulation film at least on the regioncorresponding to the reflection display section, the insulation filmbeing thicker in the region corresponding to the reflection displaysection than in the region corresponding to the transmission displaysection.

[0595] In other words, it is preferable that the liquid crystal displayof the present invention is arranged in such a manner that it includesan insulation film on one of the smooth substrates sandwiching theliquid crystal layer, and the insulation film is made thinner in aregion corresponding to the transmission display section than in aregion corresponding to the reflection display section, or theinsulation film is formed on the region corresponding to the reflectiondisplay section alone, and not on the region corresponding to thetransmission display section.

[0596] According to the above arrangement, a liquid crystal displayhaving at least two different thicknesses of the liquid crystal layer inthe region used for the display in the liquid crystal layer (that is, aliquid crystal display having different thicknesses of the liquidcrystal layer in the reflection display section and transmission displaysection) can be readily obtained.

[0597] Also, the insulation film not only functions as the liquidcrystal layer thickness adjusting means, but also applies a drivingvoltage to the liquid crystal layer without any loss by forming adisplay electrode on the surface touching the liquid crystal layer inthe reflection display section.

[0598] In this case, a light-reflecting film is formed, as reflectingmeans, on the substrate placed to oppose the substrate of the displaysurface side, and protrusions and depressions are provided on thelight-reflecting film. This arrangement is effective as specularreflection preventing means for the reflection display which impairsneither the resolution nor display ability of the transmission displaysection. If the insulation film is provided with the protrusions anddepressions like those provided to the light-reflecting film, alight-reflecting film having protrusions and depressions can be readilyformed.

[0599] As has been explained, in the liquid crystal display of thepresent invention, the arrangement for providing two different directorconfigurations simultaneously on different arbitrary regions used forthe display in the liquid crystal layer, that is, the alignmentmechanism, is not especially limited as long as it can provide twodifferent director configurations simultaneously on different arbitraryregions used for the display in the liquid crystal display. Examples ofthe alignment mechanism include: electrodes or applied voltages whichprovide different voltages to or generate different electric fields inthe different arbitrary regions used for the display in the liquidcrystal, an alignment film to which the alignment treatment is appliedin at least two different orientations and provided to each of thedifferent arbitrary regions used for the display in the liquid crystaldisplay, an insulation film or substrate formed to have at least twodifferent thicknesses on the regions used for the display in the liquidcrystal layer, particular kinds of liquid crystal materials, a liquidcrystal layer arrangement structured to be driven independently,polarization plates, phase difference compensation plates, or acombination of the aforementioned.

[0600] According to the present invention, satisfactory display can beshown on both the reflection display section and transmission displaysection by the aforementioned means and alignment mechanism. However, anoptimal ratio of the reflection display section to the transmissiondisplay section for showing satisfactory display varies depending on thedesired display, such as color display or monochrome display, or whetherthe display is shown mainly by the reflection display or transmissiondisplay.

[0601] In the liquid crystal display of the present invention, in casethat both the reflection display section and the transmission displaysection show color display, it is preferable that an area of thereflection display section accounts for 30% or above and 90% or less ofa total of areas of the reflection display section and the transmissiondisplay section.

[0602] According to the above arrangement, satisfactory color displaycan be shown both in the reflection display section and transmissiondisplay section.

[0603] Also, it is preferable that the display content is not invertedin the reflection display section and transmission display section fromthe standpoint of the visibility. This is because, if the displaycontent is inverted in the reflection display section and transmissiondisplay section under the circumstance where the lighting environmentchanges or such a change is hard to predict, a contrast ratio of thedisplay changes considerably with the luminance of the ambient light.Such a change in the contrast ratio is deemed as a similar phenomenon tothe wash-out in terms of the visibility, thereby deteriorating thevisibility considerably.

[0604] Thus, to secure the visibility, it is very important that thetransmission display section and reflection display section show thelight display simultaneously, and the transmission display section andreflection display section show dark display simultaneously.

[0605] Thus, the liquid crystal display of the present invention isarranged in such a manner that when the transmission display sectionshows the light display, so does the reflection display section, andwhen the transmission display section shows the dark display, so doesthe reflection display section.

[0606] According to the present invention, the reflection displaysection can show the light display when the transmission display sectiondoes so, and the reflection display section shows the dark display whenthe transmission display section does so by changing the alignmentmechanism or the thicknesses of the liquid crystal layer. In particular,according to the present invention, even if the display content invertsin the reflection display section and transmission display section if nocountermeasure is taken, both the sections readily can show the samekind of display by controlling the overwriting of the display content inthe reflection display section and transmission display sectionindependently by employing the display content overwriting means as thealignment mechanism. Thus, according to the above arrangement, there canbe offered an effect that satisfactory visibility can be secured.

[0607] Further, it is preferable that the liquid crystal display of thepresent invention is arranged in such a manner that the liquid crystallayer is made of liquid crystal composition prepared by blending adichroic dye with liquid crystal. If the liquid crystal layer is made ofliquid crystal composition prepared by blending a dichroic dye withliquid crystal, an amount of absorbed light can be optimized in each ofthe reflection display section and transmission display section.

[0608] It is effective to adopt a method of using the birefringence orpolarization rotation phenomenon using the polarization plate as thedisplay method for showing satisfactory display on both the reflectiondisplay section and transmission display section.

[0609] For this reason, it is preferable that a polarization plate isprovided to at least one of the pair of substrates on a surface whichdoes not touch the liquid crystal layer.

[0610] According to the above arrangement, since optimal birefringencecan be set in each of the reflection display section and transmissiondisplay section, a satisfactory display can be shown on each. Here, inorder to realize sufficient display reliably in the transmission displaysection in a liquid crystal display adopting the polarization platemethod in the reflection display section and having differentthicknesses of the liquid crystal layer in the reflection displaysection and transmission display section, a polarization plate has to beprovided in the transmission display section on the light incident sidein addition to the one provided on the display surface side.

[0611] Also, in the liquid crystal display furnished with thepolarization plate, to switch the display, it is preferable that anamount of change of the phase difference in the light caused by a changein the alignment in response to a voltage applied to the liquid crystallayer be set suitably for the light passing through liquid crystal layerand returning through the same in the reflection display section, andsuitably for the light passing through the liquid crystal layer in thetransmission display section.

[0612] For this reason, it is preferable to arrange the liquid crystaldisplay of the present invention in such a manner as to further comprisevoltage applying means for applying a voltage to the liquid crystallayer in such a manner that display light on the reflecting means of thereflection display section has a phase difference of approximately 90°between the light display and the dark display, and so that displaylight going out from the liquid crystal layer in the transmissiondisplay section has a phase difference of approximately 180° between thelight display and dark display.

[0613] In this case, it is preferable that the liquid crystal layer isaligned with a twist between the pair of substrates at a twist angle ina range between 60° and 100° inclusive, or in a range between 0° and 40°inclusive.

[0614] When the liquid crystal is assembled in such a manner that theliquid crystal layer is aligned with a twist between the pair ofsubstrates at a twist angle in a range between 60° and 100° inclusive, achange of the almost rotatory polarized light along the twist of thedirector configuration of the liquid crystal can be used for the displayin the liquid crystal layer in the transmission display section, whereasin the refection display section, a change of the polarized lightcontrolled by the optical rotatory polarization and retardation can beused for the display.

[0615] When the liquid crystal is assembled in such a manner that theliquid crystal layer is aligned with a twist between the pair ofsubstrates at a twist angle in a range between 0° and 40° inclusive, achange of the retardation can be used for the display in the liquidcrystal layer both in the transmission display section and reflectiondisplay section.

[0616] Also, in the liquid crystal display of the present invention,satisfactory display can be shown even if the director configuration ofthe liquid crystal is only changed along an in-plane orientationparallel to the substrates.

[0617] To be more specific, the liquid crystal display of the presentinvention may be arranged in such a manner that the liquid crystaldisplay element shows the display by changing the director configurationof the liquid crystal layer by rotating liquid crystal molecules inparallel with the pair of substrates in at least one of the reflectiondisplay section and the transmission display section.

[0618] Further, in the present invention, the drawback of the in-planeswitching method, that is, low light utilization, can be overcome bypositively exploiting for display, as reflection display, theinsufficient director configuration of the liquid crystal that causesthe low transmittance. In other words, the liquid crystal display of thepresent invention may be arranged in such a manner that the liquidcrystal display element includes, in one of the reflection displaysection and transmission display section, voltage applying means forgenerating an electric field in the liquid crystal display along anin-plane direction of the pair of substrates.

[0619] The liquid crystal layer may be aligned either in parallel withthe display surface like in most of the conventional cases, orperpendicular to the display surface. In other words, the liquid crystaldisplay of the present invention may be arranged in such a manner thatat least one of the pair of substrates includes a vertical aligningalignment film on a surface touching the liquid crystal layer at aregion corresponding to at least one of the reflection display sectionand the transmission display section.

[0620] When the vertical aligning alignment film is provided to thesubstrate and the liquid crystal is aligned perpendicular to thesubstrates in the above manner, there can be offered an advantage that adisplay contrast ratio can be improved, which has an advantageous effectin showing satisfactory display on the liquid crystal display.

[0621] In addition, when color display is shown on the liquid crystaldisplay of the present invention, not only the liquid crystal layer, butalso design of the color filter layer is critical, which plays animportant role in color reproduction. According to the study of theinventors of the present invention, the liquid crystal display of thetransflective type includes two styles.

[0622] One is a style that mainly shows the transmission display ingeneral use and uses the reflection display supplementarily, so that thewash-out can be prevented under the lighting environment where theambient light is too strong, and therefore, this style can be used indiversified lighting environments compared with displays of the luminoustype and liquid crystal displays which show transmission display alone.The other is a style that mainly shows the reflection display in generaluse, thereby exploiting the advantage of the reflection display that thepower consumption is small, and turns ON the lighting device known asthe back light under the circumstances where the lighting is too weak,and therefore, like the former style, this style can be also used indiversified lighting environments.

[0623] In the former style, (the style showing the transmission displaymainly), by providing a color filter having a transmission color atleast to a region corresponding to the transmission display section in aregion forming the display region of each pixel on one of the pair ofsubstrates, it has become possible to provide a liquid crystal displaywith excellent visibility, capable of showing high-resolution colordisplay while using both the reflected light and transmitted light forthe display.

[0624] When the color display is shown in the above manner, it iseffective if the color filter having a transmission color is provided atleast to the transmission display section in each pixel, and thereflection display section either is not provided with a color filter,or is at least partially provided with a color filter having the samebrightness as the color filter provided to the transmission displaysection, or with a color filter having a transmission color brighterthan that of the color filter provided to the transmission displaysection.

[0625] This is because when the color filter used for the transmissiondisplay section is used for the reflection display section directly, thebrightness becomes insufficient. Thus, when showing the color display inthe reflection display section, the brightness can be compensated byeither forming in the reflection display section a region having nocolor filter, or providing the reflection display section with a colorfilter having a transmission color brighter than the transmission colorof the color filter provided. Consequently, the color display can beshown in the reflection display while securing necessary reflectance forthe reflection display section.

[0626] Since the display light passes through the color filter twice inthe reflection display section, it is preferable to use a color filterhaving a transmission color brighter than the one in the transmissiondisplay section for the reflection display section.

[0627] Also, in the former style mainly using the transmission display,when the reflection display section is arranged to have a region whereno color filter is formed, a display voltage signal necessary for thetransmission display is a signal suitable for the color display, andwhen the color filter is not used at all in the reflection displaysection, a display voltage signal necessary for the transmission displayis a signal suitable for the monochrome display. Thus, in the case whereno color filter is provided in the reflection display section, thepercentage of the contribution of the pixels of respective colors to thebrightness is in proportion to the luminous transmittance in respectivecolors in the transmission display section, but it is equal in thereflection display section. Hence, in the case where no color filter isprovided in the reflection display section, it is preferable to changethe area of the portion of the reflection display section where thecolor display is not shown in accordance with the luminous transmittancein the color of each color filter used for the transmission display.

[0628] In the latter style (the style mainly using the reflectiondisplay), by providing a color filter having a transmission color atleast to a region corresponding to the reflection display section in theregion forming the display region of each pixel on at least one of thepair of substrates, it has become possible to provide a liquid crystaldisplay with excellent visibility and capable of showing high-resolutioncolor display and using both the reflected light and transmitted lightfor the display.

[0629] When the color display is shown in the above manner, it iseffective if the color filter having a transmission color is provided atleast to the reflection display section in each pixel, and thetransmission display section either is not provided with a color filter,or is at least partially provided with a color filter, having atransmission color with chroma as good as or better than the chroma ofthe transmission color of the color filter provided to the reflectiondisplay section.

[0630] In this style mainly using the reflection display, when thetransmission display section shows the monochrome display by omittingthe color filter, the transmission display section can be made smallerbecause the light transmittance increases. Accordingly, a larger areacan be secured as the reflection display section, and as a consequence,more satisfactory display can be obtained in the reflection display inthe normal use.

[0631] In this style mainly using the reflection display, thecontribution of the monochrome display in the transmission displaysection of each pixel to brightness can be set adequately inconsideration of the luminous transmittance by changing the area of thepart of the transmission display section where the color display is notshown, in response to the luminous transmittance in each color of thecolor filter used for the reflection display.

[0632] Also, as has been explained, since the liquid crystal display ofthe present invention has the reflection display section, it renders thecharacteristics of the conventional liquid crystal display of thereflection type, namely, small power consumption. However, if powerconsuming illumination light is kept turned ON, the power consumptionundesirably increases.

[0633] Thus, it is preferable to arrange the liquid crystal display ofthe present invention in such a manner as to further comprise a lightingdevice for emitting light to the liquid crystal display element frombehind, the lighting device also serving as display surface luminancechanging means for changing luminance on the display surface.

[0634] According to the above arrangement, satisfactory visibility isrealized while reducing the power consumption by changing the luminanceon the display surface by-means of the lighting device.

[0635] In this case, it is preferable that the lighting device changesthe luminance on the display surface in response to adapted luminance insuch a manner as to attain perceived brightness ranging from 10 brilsinclusive to 30 brils exclusive.

[0636] The perceived brightness is determined by the adapted luminanceand the luminance on the display surface. Here, to realize satisfactoryvisibility while reducing the power consumption, it is very preferable,if, in changing the brightness of the display surface to attain theforegoing perceived brightness, the lighting device changes its ON/OFFstate or luminance in response to the display content on the liquidcrystal display and the adapted luminance which varies with the visualcircumstances such as the lighting. In particular, in case that thelighting device is controlled from outside the liquid crystal displayelement by pressed coordinate detecting type input means, such as atouch panel, the above effect becomes more noticeable.

[0637] In addition, according to the above arrangement, the visibilitycan be improved where the transmission display is mainly responsible forthe display. Thus, there can be offered an effect that satisfactoryvisibility can be realized with reduced power consumption.

[0638] The liquid crystal display of the transflective type of thepresent invention is particularly advantageous in that the pressedcoordinate detecting type input means, such as a touch panel, can beused more readily compared with liquid crystal displays of thereflection type which uses a so-called front light. Hence, to provide alow-power consumption liquid crystal display incorporating the inputdevice, it is effective to realize satisfactory display on the displayof the transflective type using the pressed coordinate detecting typeinput means.

[0639] In other words, it is preferable that the liquid crystal displayof the present invention further comprises pressed coordinate detectingtype input means, superimposed on a display surface, which, whenpressed, detect a pressed coordinate position.

[0640] Further, in case that such pressed coordinate detecting typeinput means is used, whether the viewer is using the display or not canbe readily detected by a signal from the pressed coordinate detectingtype input means. Thus, to realize satisfactory visibility whilereducing the power consumption, it is effective to change the luminanceon the display surface by changing the luminance of the lighting device(which affects overall power consumption of the liquid crystal display),or to change the director configuration of the liquid crystal, inresponse to the above signal from the pressed coordinate detecting typeinput means.

[0641] For this reason, it is preferable that the liquid crystal displayof the present invention further comprises pressed coordinate detectingtype input means, superimposed on the display surface, which, whenpressed, detect a pressed coordinate position, wherein the lightingdevice changes the luminance on the display surface in association withan output signal from the pressed coordinate detecting type input means.

[0642] Also, it is preferable that the liquid crystal display of thepresent invention further comprises pressed coordinate detecting typeinput means, superimposed on a display surface, which, when pressed,detect a pressed coordinate position, wherein the alignment mechanismchanges the director configuration of the liquid crystal layer in atleast one of the reflection display section and the transmission displaysection in association with an output signal from the pressed coordinatedetecting type input means.

[0643] Moreover, it is preferable that the liquid crystal display of thepresent invention further comprise pressed coordinate detecting typeinput means, superimposed on a display surface, which, when pressed,detect a pressed coordinate position, and a polarization plate, thepolarization plate, the pressed coordinate detecting type input means,and the liquid crystal display element being provided in that order.

[0644] According to the above arrangements, an effect that a low-powerconsumption liquid crystal display incorporating the input device can beprovided, which uses birefringence for the display, and which includes apolarization plate and pressed coordinate detecting type input means. Inaddition, satisfactory visibility can be attained because thepolarization plate also absorbs unwanted reflected light from thepressed coordination detecting type input means.

[0645] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A liquid crystal display comprising: a liquidcrystal display element having a pair of substrates, to which alignmentmeans are provided to their respective opposing surfaces, and a liquidcrystal layer sandwiched by said pair of substrates; an alignmentmechanism for providing at least two different director configurationssimultaneously on different arbitrary regions used for display in saidliquid crystal layer; and reflecting means provided to at least one ofsaid different arbitrary regions showing different directorconfigurations, wherein said different arbitrary regions showingdifferent director configurations are used for a reflection displaysection for showing reflection display and a transmission displaysection for showing transmission display, respectively.
 2. The liquidcrystal display of claim 1, wherein said alignment mechanism serves asdisplay content overwriting means for overwriting a display content withan evolution of time.
 3. The liquid crystal display of claim 1, whereinsaid alignment mechanism is said pair of substrates of said liquidcrystal display provided with said alignment means; wherein saidalignment means is provided such that, in a region of at least one ofsaid substrates touching a region of said liquid crystal layer used fordisplay, at least two different director directions are imparted to adirector configuration of said liquid crystal layer at an interface withsaid region of said substrate.
 4. The liquid crystal display of claim 1,wherein an area of said reflection display section accounts for 30% orabove and 90% or less of a total of areas of said reflection displaysection and said transmission display section.
 5. The liquid crystaldisplay of claim 1, wherein, when said transmission display sectionshows light display, said reflection display section also shows lightdisplay, and when said transmission display section shows dark display,said reflection display section also shows dark display.
 6. The liquidcrystal display of claim 1, wherein said liquid crystal layer is made ofliquid crystal composition prepared by blending a dichroic dye withliquid crystal.
 7. The liquid crystal display of claim 1, furthercomprising a polarization plate provided to at least one of said pair ofsubstrates on a surface which does not touch said liquid crystal layer.8. The liquid crystal display of claim 7, further comprising voltageapplying means for applying a voltage to said liquid crystal layer insuch a manner that display light on said reflecting means of saidreflection display section has a phase difference of approximately 90°between the light display and the dark display, and display light goingout from said liquid crystal layer in said transmission display sectionhas a phase difference of approximately 180° between the light displayand dark display.
 9. The liquid crystal display of claim 7, wherein saidliquid crystal layer is aligned with a twist between said pair ofsubstrates at a twist angle in a range between 60° and 100° inclusive.10. The liquid crystal display of claim 7, wherein said liquid crystallayer is aligned with a twist between said pair of substrates at a twistangle in a range between 0° and 40° inclusive.
 11. The liquid crystaldisplay of claim 1, wherein said liquid crystal display element showsthe display by changing the director configuration of said liquidcrystal layer by rotating liquid crystal molecules in parallel with saidpair of substrates in at least one of said reflection display sectionand said transmission display section.
 12. The liquid crystal display ofclaim 11, wherein said liquid crystal display element includes voltageapplying means for generating an electric field in said liquid crystallayer along an in-plane direction of said pair of substrates in one ofsaid reflection display section and said transmission display section.13. The liquid crystal display of claim 1, wherein at least one of saidpair of substrates includes a vertical aligning alignment film on asurface touching said liquid crystal layer at a region corresponding toat least one of said reflection display section and said transmissiondisplay section.
 14. The liquid crystal display of claim 1, wherein, inat least one of said pair of substrates, a region corresponding to saidreflection display section is thicker than a region corresponding tosaid transmission display section.
 15. The liquid crystal display ofclaim 14, wherein at least one of said pair of substrates includes aninsulation film at least on the region corresponding to said reflectiondisplay section, said insulation film being thicker in the regioncorresponding to said reflection display section than in the regioncorresponding to said transmission display section.
 16. The liquidcrystal display of claim 1, wherein, on one of said pair of substrates,among regions making up a display region of each pixel, at least aregion corresponding to said transmission display section is providedwith a color filter having a transmission color.
 17. The liquid crystaldisplay of claim 16, wherein, among regions making up said displayregion, at least part of a region corresponding to said reflectiondisplay section is provided with a color filter having brightnessequivalent to brightness of said color filter provided to the region ofsaid substrate corresponding to said transmission display section. 18.The liquid crystal display of claim 16, wherein, among regions making upsaid display region, at least part of a region corresponding to saidreflection display section is provided with a color filter having atransmission color brighter than the transmission color of said colorfilter provided to the region of said substrate corresponding to saidtransmission display section.
 19. The liquid crystal display of claim16, wherein a part of said reflection display section does not showcolor display, and an area of said part is set in accordance withluminous transmittance of the transmission color of said color filter.20. The liquid crystal display of claim 1, wherein, on one of said pairof substrates, among regions making up a display region of each pixel,at least a region corresponding to said reflection display section isprovided with a color filter having a transmission color.
 21. The liquidcrystal display of claim 20, wherein, a part of said transmissiondisplay section does not show color display, and an area of said part isset in accordance with luminous transmittance of the transmission colorof said color filter.
 22. The liquid crystal display of claim 20,wherein, among regions making up said display region, at least part of aregion corresponding to said transmission display section is providedwith a color filter having a transmission color with chroma at least asgood as chroma of the color filter provided to the region correspondingto said reflection display section.
 23. The liquid crystal display ofclaim 1, further comprising pressed coordinate detecting type inputmeans, superimposed on a display surface, which, when pressed, detect apressed coordinate position.
 24. The liquid crystal display of claim 1,further comprising a lighting device for emitting light to said liquidcrystal display element from behind, said lighting device also servingas display surface luminance changing means for changing luminance on adisplay surface.
 25. The liquid crystal display of claim 24, whereinsaid lighting device changes the luminance on said display surface inresponse to luminance of an observer in such a manner as to attainperceived brightness ranging from 10 brils inclusive to 30 brilsexclusive.
 26. The liquid crystal display of claim 24, furthercomprising pressed coordinate detecting type input means, superimposedon said display surface, which, when pressed, detect a pressedcoordinate position, wherein said lighting device changes the luminanceon said display surface in association with an output signal from saidpressed coordinate detecting type input means.
 27. The liquid crystaldisplay of claim 1, further comprising pressed coordinate detecting typeinput means, superimposed on a display surface, which, when pressed,detected a pressed coordinate position when being pressed, wherein saidalignment mechanism changes the director configuration of said liquidcrystal layer in at least one of said reflection display section andsaid transmission display section in association with an output signalfrom said pressed coordinate detecting type input means.
 28. The liquidcrystal display of claim 1, further comprising pressed coordinatedetecting type input means, superimposed on a display surface, which,when pressed, detect a pressed coordinate position when being pressedand a polarization plate, said polarization plate, said pressedcoordinate detecting type input means, and said liquid crystal displayelement being provided in that order.
 29. The liquid crystal display ofclaim 1, wherein said alignment mechanism is a plurality of voltageapplying means for applying a voltage to said liquid crystal display,each of said plurality of voltage applying means being electricallyisolated between said reflection display section and said transmissiondisplay section, so that a voltage is applied to each of said voltageapplying means separately in said reflection display section and saidtransmission display section.
 30. A liquid crystal display comprising aliquid crystal display element having a pair of substrates, to whichalignment means are provided to their respective opposing surfaces, anda liquid crystal layer sandwiched by said pair of substrates, wherein: aregion used for display in said liquid crystal layer is composed ofregions having at least two different thicknesses of said liquid crystallayer; said regions having at least two different thicknesses are usedfor a reflection display section and a transmission display section,respectively; reflecting means is provided at least to said reflectiondisplay section; and the thickness of the liquid crystal layer isthinner in said reflection display section than in said transmissiondisplay section.
 31. The liquid crystal display of claim 30, whereinsaid alignment mechanism is said pair of substrates of said liquidcrystal display provided with said alignment means; wherein saidalignment means is provided such that, in a region of at least one ofsaid substrates touching a region of said liquid crystal layer used fordisplay, at least two different director directions are imparted to adirector configuration of said liquid crystal layer at an interface withsaid region of said substrate.
 32. The liquid crystal display of claim30, wherein an area of said reflection display section accounts for 30%or above and 90% or less of a total of areas of said reflection displaysection and said transmission display section.
 33. The liquid crystaldisplay of claim 30, wherein, when said transmission display sectionshows light display, said reflection display section also shows lightdisplay, and when said transmission display section shows dark display,said reflection display section also shows dark display.
 34. The liquidcrystal display of claim 30, wherein said liquid crystal layer is madeof liquid crystal composition prepared by blending a dichroic dye withliquid crystal.
 35. The liquid crystal display of claim 30, furthercomprising a polarization plate provided to at least one of said pair ofsubstrates on a surface which does not touch said liquid crystal layer.36. The liquid crystal display of claim 35, further comprising voltageapplying means for applying a voltage to said liquid crystal layer insuch a manner that display light on said reflecting means of saidreflection display section has a phase difference of approximately 90°between the light display and the dark display, and display light goingout from said liquid crystal layer in said transmission display sectionhas a phase difference of approximately 180° between the light displayand dark display.
 37. The liquid crystal display of claim 35, whereinsaid liquid crystal layer is aligned with a twist between said pair ofsubstrates at a twist angle in a range between 60° and 100° inclusive.38. The liquid crystal display of claim 35, wherein said liquid crystallayer is aligned with a twist between said pair of substrates at a twistangle in a range between 0° and 40° inclusive.
 39. The liquid crystaldisplay of claim 30, wherein said liquid crystal display element showsthe display by changing the director configuration of said liquidcrystal layer by rotating liquid crystal molecules in parallel with saidpair of substrates in at least one of said reflection display sectionand said transmission display section.
 40. The liquid crystal display ofclaim 39, wherein said liquid crystal display element includes voltageapplying means for generating an electric field in said liquid crystallayer along an in-plane direction of said pair of substrates in one ofsaid reflection display section and said transmission display section.41. The liquid crystal display of claim 30, wherein at least one of saidpair of substrates includes a vertical aligning alignment film on asurface touching said liquid crystal layer at a region corresponding toat least one of said reflection display section and said transmissiondisplay section.
 42. The liquid crystal display of claim 30, wherein, inat least one of said pair of substrates, a region corresponding to saidreflection display section is thicker than a region corresponding tosaid transmission display section.
 43. The liquid crystal display ofclaim 42, wherein at least one of said pair of substrates includes aninsulation film at least on the region corresponding to said reflectiondisplay section, said insulation film being thicker in the regioncorresponding to said reflection display section than in the regioncorresponding to said transmission display section.
 44. The liquidcrystal display of claim 30, wherein, on one of said pair of substrates,among regions making up a display region of each pixel, at least aregion corresponding to said transmission display section is providedwith a color filter having a transmission color.
 45. The liquid crystaldisplay of claim 44, wherein, among regions making up said displayregion, at least part of a region corresponding to said reflectiondisplay section is provided with a color filter having brightnessequivalent to brightness of said color filter provided to the region ofsaid substrate corresponding to said transmission display section. 46.The liquid crystal display of claim 44, wherein, among regions making upsaid display region, at least part of a region corresponding to saidreflection display section is provided with a color filter having atransmission color brighter than the transmission color of said colorfilter provided to the region of said substrate corresponding to saidtransmission display section.
 47. The liquid crystal display of claim44, wherein a part of said reflection display section does not showcolor display, and an area of said part is set in accordance withluminous transmittance of the transmission color of said color filter.48. The liquid crystal display of claim 30, wherein, on one of said pairof substrates, among regions making up a display region of each pixel,at least a region corresponding to said reflection display section isprovided with a color filter having a transmission color.
 49. The liquidcrystal display of claim 48, wherein a part of said transmission displaysection does not show color display, and an area of said part is set inaccordance with luminous transmittance of the transmission color of saidcolor filter.
 50. The liquid crystal display of claim 48, wherein, amongregions making up said display region, at least part of a regioncorresponding to said transmission display section is provided with acolor filter having a transmission color with chroma at least as good aschroma of the color filter provided to the region corresponding to saidreflection display section.
 51. The liquid crystal display of claim 30,further comprising pressed coordinate detecting type input means,superimposed on a display surface, which, when pressed, detect a pressedcoordinate position.
 52. The liquid crystal display of claim 30, furthercomprising a lighting device for emitting light to said liquid crystaldisplay element from behind, said lighting device also serving asdisplay surface luminance changing means for changing luminance on adisplay surface.
 53. The liquid crystal display of claim 52, whereinsaid lighting device changes the luminance on said display surface inresponse to luminance of an observer in such a manner as to attainperceived brightness ranging from 10 brils inclusive to 30 brilsexclusive.
 54. The liquid crystal display of claim 52, furthercomprising pressed coordinate detecting type input means, superimposedon said display surface, which, when pressed, detect a pressedcoordinate position, wherein said lighting device changes the luminanceon said display surface in association with an output signal from saidpressed coordinate detecting type input means.
 55. The liquid crystaldisplay of claim 30, further comprising pressed coordinate detectingtype input means, superimposed on a display surface, which, whenpressed, detect a pressed coordinate position, and voltage applyingmeans for applying a voltage to said liquid crystal layer, wherein: saidvoltage applying means applies a voltage to said liquid crystal layer inassociation with an output signal from said pressed coordinate detectingtype input means.
 56. The liquid crystal display of claim 30, furthercomprising pressed coordinate detecting type input means, superimposedon a display surface, which, when pressed, detect a pressed coordinateposition, and a polarization plate, said polarization plate, saidpressed coordinate detecting type input means, and said liquid crystaldisplay element being provided in that order.
 57. The liquid crystaldisplay of claim 30, wherein said alignment mechanism is a plurality ofvoltage applying means for applying a voltage to said liquid crystaldisplay, each of said plurality of voltage applying means beingelectrically isolated in said reflection display section and saidtransmission display section, so that a voltage is applied to each ofsaid voltage applying means separately in said reflection displaysection and said transmission display section.